You can't log in with Steam on multiple systems simultaneously, either. The only issue with it and GFWL is that Netflix is tied to the Live account on the 360 and needs to be a gold account to work, otherwise this would be a non-issue with GFWL as well.
Yes, but you can login on two different machines without going through some ridiculous account transfer process. Can't do that with two XBoxes.
"The whole problem with the world is that fools and fanatics are always so certain of themselves, but wiser people so full of doubts." -- Bertrand Russell (I think...)