I keep saying I don't collect them, but I guess I do.
OK - I collect them, but the expensive ones are for USING. I've currently got 6 TLR's (3 Yashica, Rollei, Sawyers, and Haco), 2 SLR's (Komaflex,Exacta), and 30 or so fun cameras.
The Komaflex has been seeing the most action recently - mainly because it works more ergonomically with flash: It's hard to focus the baby tlr's when they have a large flash attatched. Add in the aux lenses, and the Koma forms more of a system.
On the other hand the Rollei is just perfect as it is - doesn't really need any accessories. The TLR's a re definaly smoother and more fun to use provided you accept them as they are. I've got a particular soft spot for the Y44a, which is an awesome camera for the price you can get it for. My Exacta is still away for repair :-( but I'm REALLY excited about getting out with it.
I do own a 35mm, but I can honestly say I only put 2 films through it. I've got access to good 120 kit, but it's just not as convenient. 127 is a perfect inbetween format - it feels like 120 in terms of the way the cameras work, but it's compact and light, rather than large and clunky. I can literally put a tlr in my jacket pocket. A 1930's foth derby is smaller than a modern digicam.
I mainly shoot b&w, dev at home - Efke looks awesome in this format. The local lab has done colour for me in the past, but this time I'm deving myself (something new to try). It should be pretty cheap, provided I collect a batch of 6 or so films together before I mix up the chemistry.