I had one, loved it some people around here bitch about the size, but then again that is how a true roaster is. If you cannot fit in a miata, you will not fit in a Elise or Super 7. However I am 6' tall my roommate is 6'4", and my dad is 6'5". We all own (or in my case owned) miatas. We all fit once we spent 30mins modifying the front seat. The out handles most cars on the road, and on courses like laguan seca spec miatas keep up with world challenge GT cars in terms of average lap times. There are many options like the hondas to get the horse power up on a miata such as blowing or turboing. I recommend blowing them as the bottom end is built super well as that motor was turbo'd in the 323GTX. Flyinmiata.com just came out with a new super charger kit that will shortly be out for the 1.6l miata, that makes the miata an all out power car. It uses an Eaton M62 blower that is capable of spinning at 21,000rpm, and some one already has one up to close to 400hp!
For what the miata is nothing can really out handle it. If it has Koni Yellows already you are set, you just need some sways and maybe some eibach spings. With 130k on it, it is like any honda or nissan practacly brand new.
The 90 and 91 had some bottom end issues so just make sure you take it to a knowledgeable shop when getting bottom end work.
Best of luck, and consider getting the car if it is a good deal.