It could be a feasible solution if you have access to wi-fi in the areas you plan on using Skype the most.

Even then, Skype was somewhat unstable on my n800. Okay for short calls, but I was more likely to run into trouble the longer the call lasted (but that could also have something to do with wi-fi connection quality, too). I would think twice about using it for important business conference calls, etc. But with that being said, maybe the experience will be better on the n900.