Tim Coyle posted a review of his HP x5400 Media Center Extender. His conclusions are generally positive, with the exception of some networking issues. (And Microsoft’s Matt Goyer explains that those might have been avoided if Tim had chosen hardware from the compatibility list.)
I’ve been using a Linksys Media Center Extender since last December. It works great and has really changed the way we listen to music and watch TV. I was able to justify the high price tag (SRP $299, discounted to $259) because I write about this technology, but most people can’t use that excuse.
In passing, Tim notes that Hewlett-Packard has discontinued making the extenders. He speculates that this decision was because they aren’t selling well, although Matt says that’s not so. I suspect the real reason is that HP is reorganizing its PC division and wants to concentrate on business machines and notebooks instead of low-margin consumer devices. And as Thomas Hawk points out, the imminent arrival of the xBox 360, which will include Media Center Extender features, has probably dried up the market as well.
Anyway, HP’s loss could be your gain. Try searching Froogle for x5400 extender and you’ll see some nice close-out deals on new units and demo models ($200 and $180, respectively). If the price has put you off, this might be a buying opportunity. (Disclaimer: I’ve never purchased anything from TechExcess, so I can’t recommend them. Their profile at Reseller Ratings is acceptable, but it’s based on very limited data. Caveat emptor.)
Ed Bott 
I actually bought one of the demo units from Techexpress off ebay. Unit works fine and it arrived in just a few days.
Maybe I need another one for the garage?
I don’t know why I didn’t think about when I wrote my post but I did buy my extender through TechExcess (it was a demo unit) and so far it works great.
I think you are more on the mark than I was as to why HP got out of the extender business – and the Xbox 360 is definitely a factor as well.
I had one for 10 days and could never get it to connect on a regular basis. It was extremely frustrating, because when it did connect, I loved it. All my equipment was compatible but I just could never get it to transmit from the upstairs of my Condo to the downstairs on a regular basis.