I haven't tried the 28" monitor because it suffers from the 30hz problem as well, so instead I got the 24" Ultrasharp (~$200 more on amazon) and it's amazing. It supports DisplayPort 1.2 so it can do 60hz. It supports HDMI as well, but not the newer version so you are limited to 30hz if you want to use HDMI.
http://www.amazon.com/gp/product/B00HALPPM0/ref=as_li_ss_tl?...