The page doesn't work very well without Javascript. In my opinion/experience it's better to create a page in a fully usable form without javascript first. Then write a nicer/flashier/*er interface in non-intrusive javascript ( i.e. not inline javscript on elements but in a seperate .js file )

Don't forget to include a friendly reminder "This page has features that require javascript" for the paranoid freakjobs who have javascript off ).

I see that you're pulling in: Prototype - from GoogleAPIs, YUI - from YahooAPIs, Tab.js - from Uservoice ( Who I've never heard of )

As a Tinfoil hat wearing NoScript user that's alot for me click allow on and seems very messy.

Surely all the functionality you use/need/want could be provided by Prototype OR YUI ( or my favourites Mootools or jQuery )

On the design front. Please, please, please get rid of those Image Headings that look like they're from cooltext.com in favour of a Text Header and a Text Link. The Black Border around the whole site probably isn't winning you any friends and the text layout needs some fixing.

For the section about installing the bookmarklet I would: Put a heading on it like "Get Started Now!". Change the tense of "Help me" to "Need help installing?". use a border/background-color/different font to separate it better, although a heading could do this. Align the top of it with the top of something else.

I agree on the ugly factor. A simple, temporary fix might be to center everything (after moving the "just drag.." text below the two subtitles near the logo). Some things are aligned left, some centered, doesn't flow well.

Also, the logo (specifically the font used) is very 90s. Pick something cleaner.