If you're looking for an all-in-one unit that features local file playback, along with support for Streaming services, then the Boxee Box may be an alternative for you. I had one, but recently sold it. The UI is impressive, but I experienced a few annoying playback problems with it.
I've owned a PobBox, an HTPC with XBMC, PopCorn Hour A110, AppleTV, GoogleTV with Plex, and a Roku player. I've settled with the current WDTV Live Streaming Media Player. It's not completely perfect, but it's the closest I've come to a device that supports everything I need it to support. I own five of them, and playback from SMB shares over a wired network has been flawless.
I know it's not terribly helpful to hear a response that basically says "Hey, it works great for me", but you may end up frustrated with the other players. There always seems to be one or two things that are missing, I've been buying and auctioning off players for years - in search of the perfect one. If the WDTV can't be made to work for you, the Boxee Box is probably its closest competitor.