I'm not such a fan of Rollei myself * , mostly because of the pricing and the fact that there are nearly identical options available if you're only shooting film. After all, a camera is basically a lens, a box, and some sort of focusing and/or aperture mechanism in between.
My favorite for the money is the Mamiya, but it's pricey. The budget winner is the Pentax 645N. It's new enough to get parts for, is dead-simple to use, and the optics are decent enough to where only the most anal will really care. Especially if it's in relation to 35mm/what you were shooting before. Oh, and it's inexpensive, used.
* An exception to this is their TLRs. Simple and economical. Fantastic results. I can't really tell much difference between a 8000 series and their better TLRs in actual quality. Sure, the newer and fancier model has interchangeable lenses and a bunch of bells and goodies on it, plus maybe auto-focus, but the results are very close. One was made for professionals with a work flow to deal with and the other wasn't. The film doesn't seem to care much, though.
I agree with you on the TLR's. Amazing cameras, and while developed years ago, still take great images. Rollei worked out all the "user" issues long ago, and these cameras are ergonomic and precise. The film loading is an issue - somewhat slow, to be sure. But even today, a scanned image from the TLR negative, and its hard to beat it.
With the 6000 series cameras, Rollei tried to make a conversion to the SLR setup, and until the 6003/8 series, didn't quite get it right. But as the third generation (SL66, then 6002/6, ending up at 6003/8), they got it pretty much spot on for a hybrid mech'l/elec camera. The 6003 is simpler, thinner back, removable handle, but almost all the other features. The 6008 really opens up to full professional use. But you can haul the simpler 6003 around and shoot on the street pretty readily. The lightness of the thinner back does make a difference, esp. with WLF. And you can add almost all the 6008 features onto it if you want.
The main features of the 6003/8 are the integration of all the activities into a pretty fast and flexible package. The metering is fully integrated, and while I never really felt a need for the motorized film transport, the film cassettes are just a delight: preload a couple of cassettes (they're cheap and easy) and you can change to new film roll in under 10 seconds easy. Also, I've never yet been able to beat the Rollei meter.
Each person has their own feel for a camera, but the Rollei seems to fall to hand pretty easily. While I wanted to like the Hassy 500's, I never felt at ease with them. Too many oddities, and things that just seem to need a special touch. Maybe others have different opinions.
Is a 6003/8 better than the Rollei TLR? If one likes changing lenses, or the ability to use wide angle, surely. The film loading is better, and the film flatness, one of the great unheralded strengths of this system, is superior as well. Film in the 6003/8 is just really really flat to the plate. That's one reason they are so sharp. The integration is great, and the ability to go from fully automatic, to partially auto, to fully manual is great too. For travelling, sometimes I'll take the TLR, because it is just that much smaller, and sometimes the 6003. Just depends on how much hand carrying will be done. You can haul a TLR around all day, but after a couple of hours, the 6003 is getting heavy.
With the autofocus 6008 AF, system wise, things got better but maybe not as good. Perhaps a bit too much was being asked of the system, and thus the Hy6 makes a lot of sense as the next iteration of the system. Again, the overall appraoch was repackaged, reengineered, and rethought in the Hy6 - now smaller, not much lighter, but the motor is now in the back, not the camera, so for a digital back, you aren't carrying that load. And the electronics are improved.
There are seemingly other options, but few have this level of integration and the ability to both travel light and then bulk up as a fully professional system. The Bronica, Fuji, or other SLR's have either more weight or less system integration (?), but each have their own purposes.
Of course, one has to buy into the Rollei world at the right time and in the right way. They offer packages that make a good deal of sense every once anda while, and then its wonderful. I don't know if they really believe in their asking prices for these new lenses, but most were gotten for around $2k, never more than $3k (new) for any lens, for about 5 of them.... But they aren't AF lenses either.