Oh, boy, what a loaded question! I must admit that I'm one who jumped on the bandwagon late in becoming a shameless fan of the TR-7. After a Spitfire, 2 MGB's and a Fiat Spider, I returned to Triumphs via my '78 Spitfire 1500. I bought it in '88 and kept it for 10 years. An MGB followed but when I saw my '80 TR-7 Spider at a British show in Stowe, VT, I was hooked. I bought it within a year.
I have always believed in driving sports cars, often and year-round, even in northern New England where I live. The car had 48,000 miles when purchased and now, 2 1/2 years later, has over 75,000 miles. Here's the list of replacement items I've bought because of daily running:
Starter motor
Alternator
Front bearings
Front hub and spindle [1]
Rear brake cylinders and shoes
Front disc pads
Distributor cap
Throttle cable
4 tires
Clutch plate set and clutch fork
Also, the rear window on the convertible top collapsed at the zipper. Because of the tight rear fit of the top, it was cheaper to replace the entire top rather than just the window.
Much of this was "once in a lifetime" replacement. The car left me stranded twice but repairs were affordable. Most engine parts, maintenance parts, and some body parts are available through the major distributors in the US [Moss, Vic Brit, Roadster Factory] and there are two fantastic wedge specialists: Wedgeparts in TN and The Wedge Shop in MA. Both owners have bags of knowledge and lots of critical parts.
To drive the 5-speed [Land Rover transmission and rear end] is a joy; the engine matches the tranny wonderfully. You can cruise for hours on a highway at 70-75 with no strain on the engine. The car's design means that top down driving is comfortable and invigorating; if it rains, the top can be erected easily. If you have a passenger, he or she will be comfortable in the spacious seats. While there's no shelf behind the seats, there's a fine trunk, big enough for tools and luggage.
The TR-7 also handles quite well; it's not light like the Spitfire and the steering feels heavy. However, it really clings to the road, feels more nimble than it looks with its width, and makes you want to drive all the time.
Problems in general: head gasket leakage, water pump replacement, Leyland switches and buzzy plastic interior, massive '70's styled dashboard. You should like plaid, too, because if the seats haven't been recovered, you'll see lots of it.
Mine cost the same as a comparable Spitfire, around half of a great shape TR-6, and about 1/3 of a great shape TR-3 or TR-4. I know I'm going on too long, so e-mail me if you want more information.
Jeff