I've bought Colt, but that was back in the preban days. Colt enjoys name recognition and a loyal following. Not surprisingly, resale on used Colts tend to be higher than on other brands.
If name brand means little or you aren't concerned about resale, Bushmaster for the most part are one of the best. However, with the SB23 scare and the Y2K panic, demand exceeds production and Bushmaster is pushing out over 5K a month. If you choose BM, find another which is cleaner and if you find a problem, be sure to contact their service department immediately. From what I hear, they're generally very good.
Vigilantibus et non dormientibus jura subveniunt