Been a ST holder for nearly 20 years now, but I thought the Barca game was a bit flatter than it should have been until we got the lead.
I don't know if OT is louder than Anfield regularly, I doubt either ground is amongst the best atmospheres in the country. Think the scousers have people thinking their atmosphere is always good because they hear you'll never walk alone belted on full blast on sky before every game. After that they don't seem particularly loud other, unless it's a big game. Which is the same at OT. The crowd really has to be up for it for it to be at it's best, and that's not often. Best atmosphere for me this season was Liverpool at home. Best ever for me is probably Roma at home in 2007.
In general, it is better recently then it has been in a while. It's just a tough place to get a good atmosphere going, though the singing section has helped.