I've got clipless pedals on my mountainbike (spd style), on my tandem (campus pedals=spd on one side, platforms on the other like noglider mentioned) and two road bikes with speedplay pedals. I've also got 3 bikes with toe clips and straps, although I rarely tighten the straps.

I find the speedplay pedals to be the best I've tried so far (of 3 types) and use them whenever I go on a planned long distance ride. I've fallen over twice, once I leaned the wrong way (leaned right after unclipping the left foot) and once trying to cross a median and got stuck in the sand.

I'm sure its all personal preference, but I'm a stronger rider (pushing and pulling on hills) when I'm clipped in to clipless pedals. It becomes second nature do get in and out of them after 3-4 rides. I just wish speedplay pedals were compatible with mtn shoes (they're not) because they are a pain to walk in. But then I don't put the shoes on to walk around, they're for riding.

Because of the ease of use of toe clips, I'm sure I'll always have a bike or two with them.