I started out using WMC however I found that it was extremely slow in loading my music (I have about 8,000 songs currently) and there is a bug in the way the XML tag handling was performed when the song tag was truncated...This often led to a nil return being issued for a search.
I switched to using iTunes and haven't looked back. Searches now are extremely fast, song loading speed has more than doubled and the dreaded XML bug is gone.
As for streaming Internet radio, I do this on a daily basis. ROKU's web-based configuration utility currently allows you to add up to ten user-defined Internet stations, simply by pasting the stream's URL into the appropriate locations on the config page. There is no pay service or otherwise required to listen to Internet radio.
I use wireless G for my network so the ROKU doesn't affect it at all....A buddy of mine uses his M1000 with wireless B however and he has never had any issues with network performance.
And for Dawtcalm:
It's true that the M2000 is much more money just for the bigger display. However the unit itself is much larger, about the same width as a normal HT component so it's more esthetically pleasing to the eye...my aforementioned buddy now wishes that he purchased the M2000 just for this reason. For some people, bigger is better after all
The guts of both units are exactly the same though...