I consider the XBox HD DVD player to be an interim solution. It's $200, which is the cheapest entry point into the HD disc market. Period. No other player currently out can touch that; either for HD DVD or Blu-Ray. I do not plan to continue using it once real players become more affordable and better made. I will get a PS3 as soon as I can find them in a store other than frickin' eBay, and hopefully there will be some compelling games for the thing by then too.
The Toshiba HD DVD players currently on the market are not that good. They are EXTREMELY slow (almost a full minute from power on to disc start, even after the f/w upgrade), and have some compliance issues. They're also a lot more expensive. By contrast the X360 player is FAST, and easy to operate.
The same goes for the Samsung Blu-Ray player. Prohibitively priced and slow, it just can't compare to the 360's player.
So really, if you want to get into the HD disc market this year then the 360 add-on is the only way to go.