Everyone in here is well aware of the awesome job that get's done with little reward - other than the next version
Ubuntu get's a lot of testing - other flavours perhaps less so.
They'd love to see more of the action here.
Xubuntu, Lubuntu could do with a bit of tlc from the forum's formidable testers.
More details on the other flavours will follow, but Xubuntu will be running at the least 1 alpha and the beta's during the developement phase, the Release Schedule will be changing following a session at UDS, once that's finalised more specific testing needs will be made available.
The tests and iso's are all there on the qa tracker as I'm sure you are aware.
(Edit - there's always something that even when you've looked at a text doc before you post thread that you forget - I didn't mean this to sound as though no-one in here does look at flavours - I have seen the odd Xubuntu, Lubuntu, Kubuntu issue. )
More Edits: Kubuntu also needs to be tested, the daily live iso's are here, and as with the other flavours, tests and images are available on the Q/A testing tracker