i suggest 2.55, too.  i haven't noticed any changed shortcut keys except adding something to the scene.  but i pretty much waited until 2.55, and i think they spent some time adding old key strokes.  there also seems to be a plethora of shortcut keys you can add using your perferences, if you really want to. 

also, the only shortcut keys i've found it necessary to remember were the ones to get around the scene (pan, rotate, etc.) and move objects.  other than that, i've always had no problem finding everything in menus and such. 

Luxrender support is there, but for some reason LuxBlend25 doesn't seem as full featured as LuxBlend for 2.49 yet.  it's better integrated and oh, so much nicer to use, but materials like glossytranslucent are missing from the one i downloaded just a week or so ago.

Yafaray support is not there yet, unfortunately.  it seems easier and quicker to use than Luxrender, so i'm hoping to use it as a workhorse, and go to Luxrender when i need a thoroughbred.