Behaviour has stated on several occasions that cash shop variants of common in-game weapons and armor will largely be alternate skins, and occasionally slightly rearranged statistics. Trading range for rate of fire, trading ammo capacity for reload time, things of that nature. No pure bonuses that are not balanced by some sort of offsetting penalty. Some players will argue that people will learn to compensate for the penalties or disadvantages, my counter-argument is that learning to compensate is called skill. Skilled players will counter the negatives and therefore benefit from the positives. Isn't that really “Skill to Win”?
Read more of Terry O'Brien's Warhammer 40K: Eternal Crusade - Cruising the Forums - The Cash Shop Debate.