Don't go ga-ga over bibs unless it really works for you. I've been perfectly happy with regular shorts, and I've done 200+ mile rides without--well...undue...soreness.

The amount you want to spend on shorts really depends on how far your ride is. For my daily commuting I've invested in cheap Performance shorts. They get washed a lot, and I only average about 60 miles a week (aside from club rides).

For my club and event rides, I definitely prefer the higher end shorts, like the PI Microsensors. Your butt may vary.