I use Printershare from Market/Googleplay (and no, this is not spam, that app really works on my Transformer Pad). To print from Gmail, start Printershare, select Gmail, then print. It's that easy. I tried Google Cloud and found, for starters, that it supported only a limited number of printers.
I am running Printershare Premium, the paid version, so am not sure if there what the limitations are between that and the paid version.
We need to print on wifi printers directly from Android. Printershare is a stopgap measure until that's possible. My Transformer Pad has replaced my laptop because it does so much more so much faster than the Windows 7 beastie I had, but there are gaps with printing being one of the biggest. Something else that would be nice: stores which rent equipment; for instance, I need a CD burner for just a couple of days to hook up to my TPad, so it seems like a waste to buy one. In short, tablets might just change the way we do computing in the next 24 months as much as the first laptops did in the late 1980's.