My Pi cost me £50 total.
for that price it'll wirelessly stream 1080p (i.e. > than the Roku), it also looks pretty darn good with the case I currently have, plus it's tiny. With an Android phone and a free app you have a very capable smart-remote which contains your entire XBMC library. It also pulls in a full scraping service for metadata which makes XBMC look great.
You'd imagine that there's a tonne of geeking out to be done but in reality it's ridiculously easy i.e. download an installer and an image and click go. Add-ons come from the repository and they're as simple to install as select to download. Non-official apps can be donwloaded to a USB stick and again, select and install. This allows you to add-on a lot of apps that for example find live-streams of sports, personally it's of little interest but for some people it isn't.