There hasnt been a flood of interesting devices probbaly because alot of things that several of us wanted to do with M4L turned out to be crippled by the M4L limitations relative to the real thing.
Yes - great for your bog standard stereo in, stereo out effect, or a device that takes midi in and makes noises - ie the kind of thigs that the market is already flooded with high quality plugins without the CPU overheads.
However, currently it doesnt seem posible to create multi channel in, stereo out devices, ie start doing wierd shit with side chaining, and all the other cool shit you can do with MAX/MSP that is rarely available in common plugins, nor (and this was a real shock) is it even possible to create a simple control interfaces for many hardware synths, because someone thought it would be a great idea in the dim and distant past of Live's MIDI development to completely block sysex, and I guess all midi apart from aftertouch, CCs and notes (with cloks being filtered out and handled deep in the bowels of live).
Which pretty much leaves only the more obscure useful things I wanted to do with it - plugins to forward automation parameters to my DMX lighting control application - which given that noone else on the planet has that application - there isnt exactly alot of benefit in releasing my efforts to anyone
Yes there are other things I want to do with it eventually (Simulate some aspects of my machine drum so I can sell the MD), but they are low priority next to just simply making music. MIDI crippling and multi-channel audio crippling were the big killers - so ironic when MAX/MSP is pretty free about audio and so is Live, and yet the two of them cant exploit this between them - WTF? Perhaps a future update - I relaly do hope otherwise I should have just written my lighting controller interface plugin directly in C++ and saved my cash. (Actually I wanted M4L for this more for the UI - the C++ part that communicates over UDP is trivial to write in a VST).
Ive seen so many others post similar remarks, that this may be the reason why with a few exacptions to dig deep into the Live integration stuff for Djing etc, we aint seeing a whole lot of mind blowing M4L plugins.