I'm not sure how useful my reply will be, but here it goes:
I started 6x6 with a Lipca Flexora TLR, which my grandfather handed down to me (it had been his father's before). I really liked it, even though it had lots of haze on the taking lens, the focus screen was dark, and the spacing was uneven. I took good shots with it. Unfortunately, however, the shutter lost its will to live, and refused all attempts at resurrecting.
Full of sorrow and anger (why did it abandon me? WHY?), I purchased a Pentacon Six TL on ebay. I was really tempted by the idea of a 6x6 SLR with sharp optics (actually, anything without haze would satisfy me), and the P6 didn't disappoint me. I quickly set the prism aside, and stuck with the brighter and more familiar waist level finder, and made sure to stick a hood on that lens. I took this setup to Brazil, and put 65 rolls of film thru it. Aside from the fact that it only took 10 shots per roll (WIDE spacing between frames) I was pretty happy with it. Looking back, I would have flocked the interior to minimize flare in some backlit shots, but otherwise I was happy.
Oh, and the P6 died on roll number 65. That would have really ticked me off, if it wasn't for the fact that I had taken it to some extreme situations (climbing/hitting/sneaking under rocks, scorching sun, etc...), and my serious shooting was over.
I have also used a rolleicord and 2nd lowest Seagull available. The seagull impressed me (the triplet lens was much sharper than I expected, and it felt much more luxurious than my Flexora).
I once handled a Hasselblad 500_and_something and a motordriven one. I was then told of all the ways one could jam the darned things, and proceed to carefully set them down. Nothing against hasseblads (I actually wouldn't mind having one), but for a clumsy guy like me, they're just too iffy.
I am now in the process of editing/printing this last batch of shots, so I won't be shooting for a little while. I am, however, already thinking of the replacement for the P6, and as of right now have used bronicas in mind. For about $500 one can buy a setup from adorama's ebay account. Doesn't sound too high.
On the other hand, I might just go with a TLR...
hope this helps.