Re: Use html in welcome widget?
I just added the Advanced Text widget (there are others similar to it), that lets you include arbitrary HTML/PHP/whatever, and used that instead.
Add Widget Logic as well, and you can display it (and any other widget conditionally, based on whether the user viewing it is logged in or not (or any number of other conditions)! Woohoo!
(both are plugins in the WP repository, BTW)