Really chuffed to see so many appreciative comments on OSM - makes it all worthwhile. Even though I've been involved with the project since the year dot (well, since 2004) every time I look at a new area I'm impressed with the rate at which people are mapping places these days.
We're just back from two days on NCN4 in South Wales (with GPS, natch) and OSM was spot on in both Swansea and Cardiff. (If I'd have thought to search for the hotel on OSM first it'd have saved half an hour of schlepping around the docks in the freezing cold, mutter mutter...) Newport could still do with a bit of mapping love - mind you it could do with a bit more NCN love too.
A few people have recently cracked the secret of making routable Garmin maps from OSM data, so you can use it as a cycling "satnav" too, should you really want to. As yet I don't believe this has been combined with the cycle-friendly stylesheet but I'm sure it won't be long.