i like a max innings limit. it makes you take in to account things like k/9 and the like since you've only got a limited number of innings in which to acquire Ks. moreover, it makes you balance relievers with starters, since relievers get less wins per IP than starters (at least in general), so if you want to load up on relievers to get more K/9, it'll cost you some Ws. likewise, more closers mean fewer innings for starters, so if you have something like 4 crappy closers eating innings, you won't have as many innings for Ws as people with 2 or 3 quality closers.
anyhow, IP limit makes the game more interesting IMO, so you should use it.