In RC1 & 2 the form field upper/lower borders are missing (sometimes just the top one depending) in IE8 in compat mode. I can change the mode to 8 and the borders are fine as expected. I have a neighbor pull up the same in IE7 and it's fine so just seems to be compat mode IE8. Sadly, most of our company is on IE8 and IT enforces compatibility mode on all intranet sites via Group Policy.
Happens in form panels, toolbars, etc.
Is there any way you can look at the form field styling in IE8 strict during this last run towards GA? I'll be your best friend...