Official figures are about: (urban) 27.7mpg; (extra-urban) 47.9mpg; (combined) 37.7mpg
I drive mine pretty hard so get a little less.
Can't remember the insurance group but it's not bad - I pay about £350 a year fully comp with legal protecting and breakdown at 35 years old with 6 years NCB, £200 excess, £50 glass excess and the car valued at £4k - that's with a modded car specialist (Adrian Flux), too.
Bad things to watch for are corrosion on the crossmember, looseness in the timing chain and well, that's about it. Maybe rust around the base of the doors on cars that have been kept by the sea and sticky calipers. Most parts are not stupidly expensive if you avoid the main dealerships, even then it's not too bad.
They don't have a huge amount of power but enough to keep you happy on a daily drive, lots of torque in low revs and they handle really well (see the comments and vid of Simon embarrasing scoobies and evos in a standard 1.8 at Japfest this year on the track).
Not a huge amount of off-the-shelf modding parts but I'm sure the engine is well tweakable to get an extra 20-30hp out of it without going turbo.
3-doors look way better than two and they can be made to look a lot nicer with some cheap, simple, tasteful mods.
edit: forgot the comparisons - the 1.5 feels underpowered but gets better MPG (obviously). After a 2.0 it will feel very lazy, especially on hills and motorways. Never driven a GTI but they are apparently much more fun to drive than any N16 model.
Some people moan about the seats being uncomfortable but I don't mind them too much though it gets a bit niggly if driving over a couple of hundred miles in one go.
