I've gotta agree on this one. Generally all I can think when I use browser-based design tools is how much faster/easier it would be for me to go into Photoshop or better, the code itself.

I think the biggest flaw in these apps is they start people with either an amateur design or a blank template instead of exposing the grids and guides that define a website (and further define the limitations of web design) right off the bat. Even though it starts as a blank page, I love Alex Maccaw's Stylo (http://styloapp.com/) because the tools are simple and familiar, they don't overburden the page I'm focusing on and it creates smart guides that show up when I've got two elements on the same plane. It's the only one of these apps I've tried that actually extends my creativity and doesn't end up taking me longer to design something I like between clunky UI elements or trying to figure out what everything does.