There are three things I fight with when using my C330.

1: Parallax correction when shooting close distance objects (flowers, small rocks, etc.). The C330-S (possibly the C330 or C330-F?) has an indicator in the finder to show you (A) where the real top of the frame is and (B) how much to compensate exposure when racking out the bellows. It adjusts to suit different lenses. I find this to be very handy considering I don't own the Paramender device.

2: No DOF preview capability. I use it all the time with my RB67, and find myself using smaller apertures "to be safe" on the C330.

3: A waist level finder requires you to be above the camera. A TLR with a waist level finder requires the camera to be lower or the photographer to be higher. Maybe I'm just too short (5'7"), but I'm considering a prism finder for my camera. Hiking is no fun in platform shoes...

In praise of the C330 line...

- The whole line of C TLR's are built like tanks.
- Many (all?) of the C TLR's have backs that accept 120 and 220 film.
- Bodies, finders, and lenses are really cheap on eBay.
- Most of the lenses are very small. I fit 2-3 TLR lenses in the same compartment that a single Pentax 35-80mm zoom fits in my small backpack.

As for changing film, I think all of the C cameras have a device that covers them film (an in-camera light trap) for lens changes. I can't say for sure. I only have a C330-S and it's been many years since I last used any other Mamiya TLR.