With PSN being down basically the first full month of a multiplier focused game did this game get to keep its large fan base and have lots of games going at once? I was going to get it about release then with servers down I snagged Portal 2 instead but I would still like to get this.. 

I'm also interested in whether it's popular or not, whether it's a good game or not, and whether it's a true SOCOM sequel or an alienating installment

Yeah would like to hear from people with the retail version, how it holds up.

I never played the original SOCOM games much, but from what I do remember this seems a bit less tactical.  It's not a bad game though if you like third person tactical shooters.  I played it a couple weeks ago and had no problems whatsoever getting into any games, and I didn't experience any lag.

Liked the beta, then rented the game and didn't really like it.

The singleplayer is meh. The online was decent, but had no way of joining a game with your friends, which made it absolutely useless for me.

Of course, I played it the day it came out (before PSN went down), so patches may have fixed it by now.

So its still populated but not better than whats already out? Well I guess thats good to know. 

I have it and have yet to play it :/ 
Also, it appears they are starting some sort of ladder tourney with prizes: http://blog.us.playstation.com/2011/06/24/socom-4-mlg-boot-camp-official-20k-ladder-announced/

It's still populated. If you want to play a game mode other than Suppression it can be difficult to find a match. As long as you are looking for some Suppression action you should easily be able to find many matches. The game isn't bad at all, but in all honesty Confrontation had a better feel. S4 is a bit generic BUT it can be fun, give it time and learn the maps.

@Rolyatkcinmai said:

The singleplayer is meh. The online was decent, but had no way of joining a game with your friends, which made it absolutely useless for me.

Of course, I played it the day it came out (before PSN went down), so patches may have fixed it by now.

They have fixed it, you can join a friend's match now. Still no lobbies though which really hurts when you are playing with your clan.

I find myself not wanting to play the game more and more.  I enjoyed the beta, however I'm just not digging the game overall now.  It's still frustrating that there is no party system what so ever.  To me, that is something that is almost mandatory in all online games these days.  What really kills me is listening to the Zipper podcast.  They seem to have excuses for everything, etc. 
 
I've been thinking about reinstalling Confrontation to be honest.  I played that game quite a bit more.
 
Overall though, there are still times when the game can be fun.  The co-op is fairly enjoyable as well.

Its good. I play it almost daily. Still waiting for them to patch in the party mode.