Yes it does respond alot better, still a touch of lag, that I think only us nerds will notice. It got me the WAF, so I am working on getting the other 4 XMBC boxes setup. So I will be ordering more FLIRC's and Harmony's this week.
I also have the Harmony 300, I downloaded the new gui/cli tool and firmware, it flashed fine. But I do not see a new xbmc setting in the flirc gui for this. Also I do not see an XBMC or Media Center PC option on myharmony.com