I like having a level cap, it adds a small amount of additional realism to RPGs because there is a limit to how powerful one individual can be, for example, it is, with a lot of training, possible to pull a double decker bus along, but it will never be possible for a human body to lift the bus up in one hand, and I can liken level caps to that sort of reasoning, there are limits to what a person can do, level caps just display these limits in a game friendly way. I mean what fun would fallout 3 be if you could have every perk?