I love TLR's (preferably 127 obviously)... Which has often led me to ponder: What happened to camera's in the 60's and early 70's to lead us to the sorry state we're in now:
Walk into a camera shop and say you're interested in taking up photography, and the salesman will say:
a) for the kind of work you're interested in you'll want a 35mm autofocus SLR with a zoom lens.
b) what kind of photography were you interested in again?
Somewhere along the line we decided that 35mm SLR was the answer, but can't quite remember what the question was.
Once upon a time there was diversity in camera's - at all levels you could choose between film formats, and camera styles, picking something that fitted you. Then the choice went away. It's now engrained in the mind set of modern photographers: I've got a komaflex slr and a rolleiflex; in use they're very similar except the SLR is heavier and noisier, yet my girlfriend (who has more photography experience than me - on modern cameras) is far more prepared to consider the Koma as a practical camera, simply because its an SLR.
The TLR has become a dinosaur, despite its superiority in many respects. The SLR crowd oftern point out that TLR's lack auto-exposure, auto-focus, motor drive etc but at the time TLR's went out of style, SLR's didn't have these features either. The new Rollei's give a hint of where TLR's could be with 40 years of development, but why can't we get a TLR with those kind of features (and more) for the price of a decent SLR.
It's a little like the cambrian(?) period in geology - there was a huge explosion in different species of animals, and then they all died of for some unexplained reason.