I went clipless not too long ago and I'll never go back. I saw my times immediately drop significantly due to the fact that you can do a complete pedal stroke (i.e. pull the pedal upwards as well). I got a pair of ultegra pedals for $120 and Specialized shoes for $100 (but you can get pedals for cheaper, but at my LBS I couldn't find shoes for too much cheaper than that). The only downfall I can see is that it's harder to commute with the clipless (as opposed to platforms where you can wear regular shoes), but I guess that's what my beater is for.