In the Connect IQ SDK 3.0.4 Eclipse plugin, the Build For Device Wizard's "Finish" button is greyed out by default, even when all of the valid choices from the last build are displayed. You have to change one of the fields (such as Device), even if you're "changing" the value to what it already is. This is a small issue but a little annoying if you rebuild a lot.
Tried an older SDK/plugin (2.4.2) (previously installed on a different computer) and it has the same problem, so it doesn't seem to be a regression.