they are heavy yes, but weight isnt the be all and end all of handling. I could mention something about the M5 beemer being a bloater with great handling but i think my point is made. Not that im saying it will handle like an elise or anything, and they are getting on now, so the suspension is shot on a lot of them, new shocks, springs, bushes and maybe whiteline ARB's will make a big difference.
Power wise, its reasonably common for these cars to be running in safety boost (7psi and retarded ignition) without the owner knowing. This will make the car a LOT slower, my advice is to test drive a few to get an idea what a good one is like.
Biggest weakness on these cars are the autoboxes, if you have an auto it will almost certainly fail, aftermarket ATF coolers help, but they still blow up.
Check theres no blue smoke from the exhausts, smoking on boost can be indicative of failing PCV valves, or failing turbo's, or of course failing rings. If theres blue smoke after a good while of idling (10 mins or so) then the turbo seals are almost certainly shot.
What they say is right, if the turbo's give out then its an engine-out job to replace them. They are known to last 150k or more with good servicing though.
edit - just for good measure, here's a pic of mine
edit2 - as for the fuel consumption, they are thirsty if you have a heavy right foot but what do you expect, quite reasonable on a run though, 30mpg is possible. Expect an average of about 20mpg maybe a bit less.