I've got one (well, two, and a whole crudload of optics), but i've only so far used it on my 7D, not film.
Points to note:
Bodies, there's currently 4 styles:
Bellows: Lensbaby original, Lensbaby 2.0, Muse, Spark are all the same. The first two are fixed-lens, the last two are optic-swap. Frankly, the spark was just a Muse in a new package. They all work the same, as mentioned previously, handheld-only.
Bellows with lock: 3G and Control Freak. Same as the bellows, you can swing it any way you want, but then you can lock it and fine-tune it exactly how you want, great for tripod and macros. The 3G was even available in MF (like P67, with a 100mm lens). Control Freak is the newer 'optic swap' version, 35mm only. I started with Muse and liked it so much I bought a Control Freak. Been meaning to on-sell the Muse but too lazy.
Ball: Composer and Composer Pro (same thing, just black. Maybe metal). Also in 'Tilt Transformer' style (where the front bit comes off or something) to use Nikon F lenses on digital mirrorless.
Straight: Scout. Just a simple back/forward focussing to keep the 'sweet spot' in the centre.
Optics: 50mm Plastic, Single Glass, Double Glass (in order of increasing "traditional" IQ), Soft Focus, Pinhole/Zoneplate. 12mm Fisheye, 35mm, 80mm. I've got all but the 12/35/80mm versions.
Then there's all the accessories: wide, ultrawide, tele, macro closeup, they all work as well as any others. I've had good success with the Lensbaby Macro lens mounted on my EF 50/1.8 II with a step-down ring.
Now, with metering, you're going to have a problem with TTL (at least, I did). On my digital I only really use Live-View, the metering is always correct. Using the Viewfinder the metering can be off by a few stops (at least with digital I can chimp). Same as using a normal Tilt-Shift lens can throw off the metering. So either use an external meter, or TTL meter with it centered, and AE-lock or transfer the values to Manual metering. Or maybe you're lucky and moving it won't mess with your TTL metering.
As to whether or not you like 'the look' is totally up to you. To me it's the same as Fisheye, or really narrow DOF portraits (even birds), or 'miniature' using a Tilt-lens the 'wrong' way. Sometimes it's good, sometimes it really adds to the photo, sometimes it gets very very overused (like those mobile-phone pictures that just blur the top/bottom of a picture to make it look like a tilt-lens was used to make it look miniature. Those shit me sometimes).
But hey, if you like it, do it. It's just like porn on the internet, no matter what you make there's someone, somewhere, who'll like it...