Buells are peculiar...and they like an owner who is not afraid of maintenance and constant attention. I have more than a few friends that are former Buellers, including me. All of ours were tubers (1200cc EVO engines, full tube frames, the first generation). They were a ton of fun but they shake, rattle and roll. My S3 was probably the best bike I ever owned for getting on at the crack of dawn and having fun carving the corners. Lighting up that beast at dawn did alot to really get the adrenaline going! Reasonable power level with lots of Torque low and a wicked exhaust note. Set it up in third gear, keep the revs high and tear up the road. I never travelled far from home on it...100 miles was at the limit of my comfort level when it came to reliability, besides the Electra Glide was much better suited for this...It was a great Sunday morning asphalt shredder.
The new ones are more compact and have an updated form of the EVO/Lightning engine. A bit different animal than the 1st generation but has the same genes. They always felt too small to me. I like the Ulyses (sp?) alot but the seat height is a bit high. They don't hold any value to speak of, so make sure you like it before you buy it.
I sold my 2000 S3 with 17K on it for $3,500 in July (I was second owner). This is a bike that retailed at over 13K...

and it was in beautiful shape, PM wheels, new tires, fresh spring tune up, shop manuals, cover, extra parts, etc. I miss it sometimes, but with the MM I don't even really make time to ride the Glide as much as I'd like to. If I was looking to get another, I'd look for a cheap tuber, better bang for your buck.
If you like it, buy it. They can't really be compared to the current crop UJM Superbikes which are badazz in their own right.
Buells are old school street hooligans in the purest sense.
(Rare? I never ran across another Buell exactly like mine, and rarely saw another on the road during 3 years of ownership)