How important is 1080p upscaling in a receiver?

I bought a pioneer vsx-821-k, but after checking online I see that the 921 has 1080p upscaling. How important is this? I will mostly be using my TV with my home theatre pc, and watching HD channels, but will non HD channels look worse? Should I take it back and pay the extra 50 bucks to get the receiver with the anchor bay 1080p upscaling?