I have had one for a couple of years now and still love it. Insurance is cheaper than you think, mine is £375 via Tesco, fully comp as a third car with them.
The hardtops are OK, but you need to have somewhere to store it when you are not using it and they dont fit that well, also it means on cracking winter days you can put a warm hat on and go roofless easily. Drive one in a blizzard and you will know how much fun there is to be had in winter withut a roof!
Mechanically they are fine, a few bits rust here and there on the older ones though in the engine bay. Just keep on top of it and tidy it up.
The roof, if you get the standard PVC one looks a bit naff, but I put a new mohair one on mine last year for £280 and it really does look 100% better.
The engine is orignally out of the Coupe then into the b and then into the Punto HGT so its a fairly good old thing. Needs to be revved to get it to go though and the only downside of that is that it can be a bit dull to drive sedately, its either nuts off or nothing.
Grip is superb though, if you get some good tyres on it, bit handling can be a bit wayward over bumps for the unwary.
Running costs are fine if you can do most of it yourself but you will have to wait for parts to arrive at the dealers if its a b special part. General stuff like brakes etc are Punto MK1.
I personally don't like DTR as they were unhelpful when I tried to use them, but most people say they are OK but a bit pricey. If you want special bits for it then try ebay Germany (
www.ebay.de) as there are loads of things on there for them (which is where I got my hood).
Lastly, its a bit tricky at junctions to turn left with the hood up unless you position yourself straight, but you soon learn!