I tried a poncho after seeing how popular they are in Vietnam (where most people get around on a scooter/motorbike or on a bicycle).

I'm not so keen on them. They don't stop water from underneath (wheels, road, side-blown rain) and don't cope with the wind well.

I used a Vietnamese vinyl poncho for a while and it was handy for short showers (really quick to throw over everything) but in the end I went back to rainjacket +/- rainpants (or just thermals). My favourite is made of Epic material and is very breathable, waterproof enough and keeps me warmer and dryer than the goretex, PU-proofed nylon and DWR Pertex tops I have tried.