Considering a 5 week month for a system the just launched I would say it is bad performance. That is around 50k a week very very weak for the big dog of console gaming. The PS3 should be riding a launch momentum wave like the 360 and Wii.
again, 360 sold less during the launch... And again, it costs 50% more.
of course a lot of that comes from the fact that MS couldnt produce 360 in serious numbers, and another fact that they had to keep replacing units, but thats MS's problem... Just an reason, not an excuse.