I resisted signing up to MapMyRide because it wanted me to connect using FriendFace, but that aside, I've heard good things about it. Maybe I should give it a try.
I've previously used RunKeeper, which suffered the same GPS glitches as I experienced with Strava, except that you could easily amend the track to make it correspond with your actual route.
I thought I'd try Strava because lately I've heard so many people banging on about how wonderful it is*, but I suppose it's only ever going to be as good as your GPS signal, and an iPhone 3GS is somewhat limited in that respect. The usefulness of an iPhone as a GPS device is also limited by battery life. Strava looks like it could be a useful/fun app if you have a Garmin or somesuch. The segments thing certainly appeals to the competitive animal in me.
d.
*I'm slightly surprised that regular users of a cycling forum are saying they've not heard of it - I'm finding it impossible to avoid hearing about it!