I've been looking at the car for a long time and I like the striking looks and rarity of the car. The only problem is that seeing as how it has a V12 engine, it gets about 17 mpg combined. Worth it?

No! It's a interesting BMW but the amount of power you get from the engine is poor.. They drive well-but I wouldn't go near one unless it was special.. The engines are not very tuneable.. I would only ever go near one if it had a m5 e39 engine and running gear in it.. 400horses is the minimum one would expect from a 5l car!
The m3 is much better.. A lovely 100hp=1l
50/50 weight distribution(or near)
6th gear
Economical if driven sensibly..(my e36 just loves motorway cruises)
You can get up to 43miles to the gallon!
Servicing is expensive on the 8series..