My Miata still has it's original battery (11 years old). Winter is almost here and it's still cranks nicely.
Yesterday was my boss's birthday. His kids bought him a nice, first-generation Miata as a present. He's delighted with it! (he's driven mine and has admired it for a long time)
One nice thing about Miata engines: they are "non-interference".
This means that if the cam belt snaps, you don't bend all the valves. So while changing the cam belt regularly is always a good idea, it's not as critical as with many other cars.
Like Scott, I have an MGB. I agree that the two cars are different. I'm not sure I like sitting in one over the other. The Miata has a roll-bar that slightly limits back-rake. I will say I prefer the smaller steering wheel on the Miata, I like the seats in the Mazda better and the pedals on the MGB are harder to heal & toe. It would be pretty simple to improve all that stuff in the MGB, but it's stock and I'm leaving it like that for now.