New UI Prototyping Tool

Am a big fan of the simplicity of Balsamiq Mockups, but ForeUI looks like a contender. Some key differentiators for me are:

• different skins that can be applied to the mockup widgets (e.g., quick change from a hand-drawn look to a Vista look with a simple click)
• there is a community growing around developing new widgets -- ForeUI has a central repository where folks can upload/share/comment on widgets
• limited simulation where you need a bit more fidelity in the prototype.