tbh i rarely enjoy any fps where you level up and get better weapons. Everyone else seems to like it so i guess it's just me but if you only play something like BC2 casually like i do, you not only have to contend with regular players knowing maps better than you, they also have much more powerful weapons, that perk thing which gives you really powerful bullets, lightweight, stopping power etc.
I liked it better in FPS's where everyone started with the same weapons to choose from. Probably the reasons TF2 is so popular(some unique weapons are more powerful, but not drastically so, or are quite well balanced).
I have no problem particularly with being able to customize your character, in fact think it is great, but only if it is available to everyone