Thanks for a great, customizable theme and great instructions!
With regards to css affecting borders:
I've noticed that there are several occurrences of what seems to be a typo in Thematic's default.css. Rather than 'border-right-color' or 'border-left-color', I keep finding 'border-right-color-value' and 'border-left-color-value'.
At least under FF 3.6 for Mac OSX, this causes the selector to be non-functional. Correcting the selector name to 'border-right-color' fixes it. Perhaps these selector names could be conformed in a future update?