Yeah, if your upload speed is restricted it would take awhile, although it runs in the background without you needing to do anything (my files took about 3 days to fully upload, although that was partially because I added another folder after two days) and of course you can use the service even while it's uploading.
To be sure, the idea of music matching (not having to upload) your files is a good one, but apparently neither Amazon nor Google could make the deals work (yet). Apple may be having more luck (although we'll have to see what their service looks life before we'll know what that means). Anyways, your small test is a good idea, and who knows, for some people holding out for Apple's service might be a good idea (or waiting to see if Google Music eventually gets that feature).
For users like me this is already a fantastic service, one that lets me shed iTunes and my iPod, which I'm thrilled about.