I've never played a game on PSN and likely never will. Not a fan of online gaming and especially not on consoles. I have purchased content on PSN though, mostly PS Classics such as FF and MGS and downloaded mandatory updates and patches, of course.
The servers for patches and content just seem incredibly slow, it takes forever to download a simple update, whether it be firmware or a simple content patch for a game.
Its frustrating, especially since a lot of it can't be put on background download.
Spending close to an hour on content in the range of 500MB-to-1GB is unacceptable for a modern service, especially when our internet speed is 25MBit per second.
Services like Steam, GOG and torrents work lightning fast in comparison.

The infamous PSN hack and maintenance are probably my only two issues I've ever had with it.

PSN always run smoothly

the outage and the leap year bug where my only issues... where i live the internet connection has good quality, so i never have problems...
then again, if people will try to play COD on launch day with other 3 million people at the same time... a few will have issues, for sure, no matter what service you use.
also, think that is old stories about the beginning of PSN, i guess it had more problems than xb live so the story carry on as a urban legend LOL

I haven't played either game personally but I hear Playstation All Stars and Twisted Metal have big problems. In those specific situations, it's probably the game and not the network that is the problem.

to anybody who has actually used psn its clear that claims like those are made by xbox fans trying to justify xbl

sure there are issues from time to time like disconnects but in my experiences there are pretty rare

btw lag with online gaming is generally dependent on actual connection speeds of the users

That is a problem with the netcode of the game. Twisted Metal improved with the updates but still has some problems in matchmaking. But All-Stars is perfect, completely lag free. PSASBR actually has the best netcode of the fighting games I have, comparing with Mortal Kombat (a bit laggy) and KOF XIII (laggy as hell).