This has been stickied Im suprised you havn't read it
Dci buyers guide
http://www.cliosport.net/forum/showthread.php?t=235704
Basicly are they worth buying? Depends what you want how much you have etc.
roughly how quick are they? 65 model has about 70hp the 80 has about 85 (they are always quicker then the real offical numbers suggest)
0-60 is better than spec top speeds about right. How quick do you deem quick are we talking on track? Theres a vid on youtube of one going to 120 on the clock which is about 110mph in real life (65hp model). There a few video of it on track as well which might help give you an idea how quick the 65 is.
How good are they on fuel? I get about 55mpg all the time (I have a long drive to work but drive very hard realy). Worst I ever get is 28 on track. I've seen 85mpg but that was going very careful.
I've seen high 60mpgs at 80mph on the Autobham (no real it is) But my speedos a bit out by about 5mph due to the fact its out anwyay and I've got the wrong sized tyres which are a bit smaller than stock but there cheaper.
whats the price range? Depend what your looking for £2k to £14k I think. What ae you looking for?