A naive mod-shift-t that calls 'float' on the window is pretty easy to
write, but its not so useful. Really, the window also has to be moved /
resized, to be noticeably in the floating layer.

wmii seems to remember the last size/position of a window before being tiled,
and restores that upon switching from tiled to floating layer.
And it's usually pretty noticeable - the tiled windows are normally reordered as a result (it's similar
to closing a window).

Perhaps file a bug report, that there's no way to float a window from
the keyboard? Then we'll be forced to rememb^h^h^ addres this before 0.3
comes out in a few weeks

Seems that a bug report already exists... (I could have read it before posting).
http://code.google.com/p/xmonad/issues/detail?id=4
It covers keyboard control of float state.
I've added a comment regarding switching focus to the floating layer, before
launching applications.

.
Thanks for the feedback! You raise some good issues. Let me just confirm
I've summarised them correctly, and the action we'll be taking:

    1) floating status should be accesible from the keyboard (will be looked at)

    2) certain apps should always be floating (to be added)

    3) which apps are floating by default should be configurable (to be added)

    4) ponder 'floating layer focus' as a simple way to ensure a window
    starts floating. (useful idea to look at)

So, stay tuned. Most of these we're already looking at, or actively
writing code for :-)

Cool.
Thanks,
Avi.

-- 
"If you are an expert in the intricacies of C++, please consider this
knowledge a kind of martial art - something a real master never uses."