i'm looking at migrating from T-Mobile to Three.
I've just got a month-by-month sim with them and for five quid less a month (£15) I get a few less talk-time 'minutes' to non-three phones, free voicemail, free calls to customer service and I don't suffer from the various data usage restrictions (no IM, VoIP etc) that T-mo have.
Also, in my tests my bandwith has gone from ~3Mb/s to ~8Mb/s

I've heard abnecdotal warnings about network coverage and quality but I heard similar horror stories about T-Mo and had no problems.

Does anyone have any up to dat experience with them?

Oh, and yes, the Three SIM card bug has definately been fixed