My observations...
Web pages are nice and snappy with:
FireFox 9 (Win7-64 and OSX Lion)
Safari 5.1 (Win7-64 and OSX Lion)
Chrome 16 (Win7-64)
Internet Exploder 9 (Win7-64)
I've seen *no* hangs or slow loading with FF/Safari/Chrome as was the norm for me prior to this beta release. Although a bit slower (as expected), web pages even load fine when using my notebook on a 3G broadband connection vs. a direct local network connection. I'm quite happy about this very-positive change!
IE9/64-bit is jerky & sluggish (no surprise - this is typical for 64-bit IE, IME).
Y-Axis graticule lines on the graphs don't show up when using IE9-64; this has always been the case for me with the JavaScript-based graphs introduced with 4.05 firmware. No big deal... this is really just cosmetic.
Safari and Chrome both exhibit an annoying white flash when changing pages.
The drop-down menus still don't work on iPhone/iPad w/ IOS 5 (but this isn't actually an Apex problem - it's due to a known bug in Mobile Safari)
Pinch/zoom no longer works with iPhone/iPad running IOS 5.0.1 This isn't too bad on iPad, but the inability to zoom in renders the Apex web pages unusable on my iPhone 4... I can't even read the outlet names on the status page. I have made a slight modification to the web code, which eliminated this problem without causing any adverse functional effects that I can see. I will continue testing some more, and if I don't find any issues with the tweak I made, I'll provide the details to Curt.