what is the advantage of the Lenny over the uC32?
Direct USB connection (no FT-232), and 99.999% Arduino Leonardo compatibility. PPS functionality. I2S support (REFCLKO).
is the Lenny 5V tolerant? (looking at the board I guess no)
Some pins are, some aren't. I haven't catalogued which are yet, but you can cross-reference with the datasheet.
what is the ETA? I am keen to get one to play with. I plan to test with different graphics boards I have from the Arduino times and other Adafruit boards e.g. NeoPixelMatrix and the LoL-Shield
That's a good question. Last I heard the fab house was shopping around for components, but I think they came in over budget so more quotes and shopping are needed by the sounds of things.
However, since it's you, I'll pop a beta-test board in the post to you so you can have a play.