The idea is good, Marcus, and Pentax know a thing or two about optics on a budget. Their digibins are small, reasonably priced, and probably give you a surprisingly good picture.
Unfortunately, they made an unforgivably stupid design decision: the digibins don't take Compact Flash or any other type of removable, compatible storage: they have inbuilt RAM, and a miserable 16MB of it is all you get. Non-upgradable, and hence darn near useless. 16MB is nothing. Even at the relatively low resolution (and thus high storage efficiency) of the Pentax digibins, it's enough to take some pictures of one bird if you are lucky. Heck - I take three 512MB flash cards with me for a day's birding and sometimes fill them up - which is greedy, I grant you, but that's almost 100 times more than the digibins provide. A sensible bare minimum would be 128MB. Back when I used to have a 1.2MP camera (similar to the Pentax) that used to be just enough if I was careful not to take too many shots.
Bottom line: don't buy the Pentax unit (which is, so far as I know, the only one on the market at present). Wait for Pentax to bring out a Mark II version that takes a standard Compact Flash card. (Or for one of their competitors to do it, of course.)