I only online game with my PS3. Very seldom do I play SP as I am very addicted to Battlefield BC and other FPS. I cannot wait for MAG (256 player online Shooter Sony is developing). I have a 5 meg cable connection and never had a speed/lag issue when it comes to game play. That being said, content download (firmware updates, game updates) on the Playstation Network is insufferably slow at times. This was not always the case, so I think it probably has to do with available bandwidth on the network, which could be upgraded at some point in the near future as users grow, especially with the upcoming release of Home, so I would not let this be a dealkiller.
As for Netflix, Zookster is right, you can use Playon to stream. The 360 just got this ability without a media server direct from Netflix, so I would bet that the PS3 is not far behind.
The internet browser works, but it is not always the most user friendly experience. Sony just added the new version of FlashPlayer, so you can now watch youtube and other streaming flash content over it. I assume the browser will be improved in an upcoming firmware. I like the fact that new fuctionality and fixes are released on a every couple of months basis. Can be a pain to download the new version every 2 months, but I have never been sorry I did it.
As for Backward Compatibility, I think the MSG4 bundle was the last way to get BC. All new 80g+ units do not have it, which leads me to believe the rumors floating around that BC can be obtained by software emulation delivered via a firmware upgrade may have some merit, and that it might be coming down the pipe for all units. I could be wrong, but that is my gut.
Blu-Ray playback is flawless and I have never had an issue. I have played regular DVDs and video quality is significantly improved with the PS3 upconversion.
I would give it a strong 9. I have no major complaints, and the few issues and gripes I had have been addressed via firmware upgrades.
One small difference between the 360 and the PS3, is that MS limits the size of DLC and patches for its games to 200 meg, Sony does not, which allows developers to offer larger, more complex add-ons to titles. This typically does not matter for ported titles, but can be a plus for platform exclusive titles. It will never be apples to apples, but if there is a PS3 exclusive title you really like, the unlimited patch size could be a positive.