Explaining Vanguard inevitably leads to explaining Vanguard's community. So, let's just start with it: yes, the game and the forums/fansites that support it are plagued with 'Fanbois' vs 'Haters' - the most heated faction warfare I have ever witnessed. Here, though, the rule of 'vocal minority' is in effect, and if you stay off of the forums and out of general chat, the majority of players are quiet and friendly (if you're not on a PvP server!).
According to unconfirmed sources like MMOGData.com, the Vanguard community is shrinking: what at launch had featured around 200k subscribers was down below 50k by May of '07. The PvP and Roleplay server populations are still rather steady, but the "normal servers" are practically ghost towns. When I created a character to explore one of those servers, I ran into another newbie who boldly stated "you're the 3rd person I've seen so far!"
Contrary to your probable expectations, I'm not going to say that this means VG is a "bad game", or that I think it is a "bad game". In fact, I think it's a rather good game, it just isn't the game it promised to be.
For example, flying mounts were expected at launch, and still only appear in the game as "rental" items. The Inquisitor class, an anti-magic tank type, was not ready for launch and still hasn't made its way into game; neither was the offensive fighter Berserker class. Explorers found whole city or hunting areas laid out, but not populated: the list goes on and on.
What is in the game now, at this moment, impresses me. Every class that I have tried in VG has its appeals both for power and for fun. For example, VG rethought the Cleric class: instead of being an exercise in heal-and-sit-and-stand-and-heal, the VG Cleric is a powerful meleer, and is expected to help in combat. Other healer-class options include the martial artist/healer Disciple, and the nuker/healer Blood Mage, who gains power when she does damage and transfers that into healing. Playing my VG Cleric, I've been able to solo and have fun bashing and smashing with the rest of the world.
The Necromancer class is another interesting twist on an old idea: the VG Necromancer has the deadly DoTs (damage over time spells) and control over the undead, but their undead pet can also be augmented via body parts - yes, body parts - that you salvage from the corpses of your enemies. There is nothing so satisfying as pulling out the shinbone of your foe and handing it to your pet.
While some feel that the world graphics are too plasticy and doll-like, I personally think that Telon is an engaging and beautiful world - and a massive one, at that. The game's horseback and boat travels are absolutely necessary for traversing the three massive continents - but like the rest of the Vanguard world, travel has done its job at sparking animosity. Die hard hardcore players were expecting a world where travel was significant - fun, but still time consuming. Before launch, it was clearly stated that Vanguard would not support a teleportation system, and that users would have to hoof it or sail it to get to where they wanted to be.
At launch, "temporary" teleporters were available for cross-continental travel. These became permanent teleporters, and more were added to transport you within the continent itself. While many players rejoiced at this, the original die hards grumbled and those who had already discarded the game for its "busywork traveling" rarely ran out to buy the game.
There were also a lot of initial problems at launch with performance and lag; players were constantly crashed to desktop, had a "black screen of death" where you lost all graphics and had to restart. Opening doors was and still is a total lagfest - boats sometimes disappear, or passengers fall off in lag. One friend quit the game in frustration after multiple crashes and the inability to traverse town - and his system was well above the required specs. (Note: this has gotten a lot better over time, but is not yet completely solved).
Despite the lack of content delivery and the performance issues, I still set out in Vanguard to have a good time - that's what gaming is all about. As stated above, my Cleric character was extremely self-sufficient and able to solo quite competently; I rarely hunted with others and explored the world on my own.
For kicks, my Cleric was created on the role-play preferred server, and I made every effort to get those around me engaged with "in-character" discussion. I had fun with my successes and a good laugh at my few failures, but all-in-all, the role-play community was fairly impressive and fun. As for lore, though, it seemed like the Vanguard lore was patched together and often hard to follow; from reviewing the official site and fansites I had a hard time figuring out whether I was supposed to follow one god or many, what and who the gods were, etc. The world itself allows for a great deal of role-play exploration, and races obviously at odds - gleaned via NPC text - could creatively work their individual stories into an overarching theme.
I explored the three continents, doing various quests that ranged from 'corny' to 'awesome' in my opinion (examples to follow). One of my least favorite quest lines in my starter town had Guard A ask me to play a trick on Guard B and stick a chicken in his room. Guard B, terrified of chickens, asked me to remove it. There was absolutely no storyline, and no fun. The starter diplomacy quests were also annoying, allowing me to choose between two shady factions, and once that choice was made I could not betray my employer. My self-decidedly lawful/good character was forced to murder, steal, and lie in the name of quest advancement.
Conversely, my favorite quest led me to discover a sleeping mace deep in a tomb haunted by undead. By collecting several drops off the undead I was able to partially awaken and obtain the mace - Adrid, Mace of Sorrow - and subsequent quests allowed me to further awaken its latent powers. I was sent to solve riddles, feed it with the sorrows of others, etc - and I had a blast progressing my new weapon.
Overall, the majority of quests that I came across after I left the frivolous starter town were fairly engaging and fun. But while I enjoyed my casual progression up to level 30, I had to be honest with the hardcore raider core: this was not a game I could ever play "full time", or even long past max level; I didn't see a big capacity for raiding, and the few hardcore raiders I met in my journey made max level and quit shortly thereafter to return to WoW or EQ, or move on to LotRO.
Of course, age does wonders for a game - look at the size of modern EverQuest, compared to the original three continents and three raid targets - but Vanguard's updates seem to be slowing down, and the promised additions (like the Inquisitor and Berserker classes, as well as ownable flying mounts) still haven't made it into the game. Customer Support has been excellent in dealing with bots and plat sellers, but game content support has slowed down with the change of hands between multiple companies.
All said and done, I would recommend Vanguard to a casual gamer. Vanguard makes a good game a couple hours a day, or only a couple days a week, but hardcore play or long-term play just aren't options, yet. Community should improve with the upcoming planned server merges, as the world once again becomes populated and playable for non-solo classes.