Everyone should own a two-seater convertible at some point in there life and that car should be a Miata!
The Miata is a fantastic car. Cheap (used anyway), reliable and amazingly fun to drive. I bought a used 1994 Miata in 1996 and have loved every minute of it. The aftermarket and enthusiast community is huge and at times overwhelming. People just _really_ love this car.
The Miata is a small car. And that's not for everyone. Only average and smaller-than-average people even find it comfortable. And trunk room is big enough for about a weekend's worth of luggage (or if you relocate the spare (standard on 99+)) a set of golf clubs. Rounding out the negative points is a lack of horsepower. As enthusiasts cars go, the Miata is short on power. But there many aftermarket options.
But the Miata shines not off the line, but in the twists and turns of everyday driving. You will long for those sweeping highway onramps and secretly smile when your passenger says "oh sh$%#" as you swing around corners at speeds insane for mere mortal cars.
With 85k miles on the clock, my Miata has been rock solid. I recently replaced the battery with some other items, but other than routine maintenance, the car's been perfect.
There's a great used market for pre-99 Miata's. If you don't need a lot of room (I have a truck for that. ;p), there's no reason you shouldn't own a Miata, at least once...