I tend to "group" a couple here, a couple there etc. etc., and then roll them one iniative # per group.
Keeps things a little simpler (i.e. the two "archers on the balcony both shoot at the same time), while not overwhelming the players.
I can't see how having everyone going on 10+ init roll makes any sense....no sense of the *chaos* of battle, reflexes, randomness etc. Once battle settles in, I may group up more and more, particularly if a "leader" jumps in and tries to coordinate things, or creatures are hightly intelligent, but "dumb" creatures I try to keep somwhat chaotic...
I also purposely have cowardly/cautious creatures delay until strong points of resistance become obvious, and then try join in the easy battle, instead of winning initiive, and then just jumping in.
Alvo