At the moment I have disabled Simplify for the users. It worked fine for me, but other were complayning that top tool bar is not working.
Those who provided details on browser and OS Issues reported the following:
Win7 (starter)+Chrome - icons are not clicable, unable to get into mailbox etc. Same machine (?), IE works fine
WinXP + Opera - toolbar not active
Win7 + Firefox - toolbar not active
Win 7 (standard)+Chrome - works fine
Since I tested the skin under Firefox for Windows 7 (pro, 64) and couple of IE version, I think that the main problem is in Java version. My biggest issue with Simplify was color picker - it may behave incorrectly after several color changes, not registering left mouse clicks. Selector circle remains "glued" to cursor. By the way, IPB color picker in ACP behaves in similar way in Firefox.
Also intial changing ofcolors is affecting some elements (like "new" boxes) which return to old color scheme after you reload the page.
Nice and clean but extremelly frustrating font choice. Why user can customise body font but not headers, user's names etc.? Since you are using different fonts (including "Yanone Kaffeesatz" for crying out loud :( ) users with different languages installed will get a mess instead of frontpage with very strange font substitutions.
Please have a look on this.
Also color picker is next to useless due to limited amount of colored elements visible. One great way to showcase it will be having colored background strip for the logo changing color.