I am eyeing the galaxy tab 2 and the unnamed toshiba tablet. Both have very similar tech specs to the xoom (10.1" same res screen, tegra 2, etc).
The xoom looks great and is certainly coming out first, but I'm willing to wait a month or two and get an equal device for a lot less $$.
Some points in the alternatives' favor:
* samsung builds and manufactures most of its own parts, so the price could be lower than xoom
* samsung already announced 16gb model, which should be cheaper
* samsung is noticeably lighter than xoom and toshiba tablet
* toshiba tablet has nice ergonomic exterior surface with interchangeable colors (meant to be durable, spill resistant, and easy to hold)
* toshiba tablet has confirmed removable battery
It will be interesting to see reviews of all 3 head to head, but I dont think you can lose with any of them. All are pretty similar in terms of size and specs.