Hmm My views:
Wii Channels - I do like the layout, but to get more functionality you have to download more channels which is a pain in the arse.
360 Blades - The Blades are a clear winner, although it is a little annoying on some days when you have music streaming or connecting to Live with the lag, but the customization is a clear win.
PS3 X-Media Bar- I haven't seen alot of this, but I must say after the 360's blades the Bar falls short.
Windows - I am sick of Windows, with out going into the same old Rants, All I will say is out of the 4, Windows tends to have the most trouble with loading up Menus on some days.