More or less what it does is provide you with some nice looking HTML templates, and a way to organize your listings using those templates. I know that @capnwes switched to Mac specifically to use Garage Sale, but this is his life and livelihood. If you are doing this as he is, it might be worth it to make the switch, as I think it's probably the best listing tool on the market right now (though not without it's flaws and idiosyncrasies), but if you are just doing this part time, I think you'd be better off learning a bit of HTML or copying some HTML templates that you like and using them yourself to build auctions. You can save templates in eBay as well (though I haven't done that so I don't know how easy it is). Unless you can thrift a mac for CHEAP, I don't think it's worth the purchase of a new computer, unless, again, this is your livelihood.