In spite of all the abysmal updates and ugly server problems, I was a Planetside junkie for years. I quit a few times, only to return like a battered wife. It just held so much promise...
There's an NDA in effect for one more day, but I am sure I'm not violating it because I have been so effusive about my experience.
During my beta experience, I have not experienced any noticeable lag issues. When I shoot someone, they get shot. There's been no odd skiing/catchup problems so far.
Also, there are no dice rolls in this game. There is base damage and range considerations - that's it. True, characters can do things like decrease the damage they take (via spec-trees), but at no point (so far) have I been so outmatched that I am ineffective.
This is - by the way - the main reason I detest World of Warcraft. I concede that there is a deep strategy at work, but any game where one high level guy can wipe out a dozen low level guys without getting hurt is a failure. It's just not my bag.
For example, I was in a round of GA over the weekend and managed to kill one guy (XXXXXX was his name) a bunch of times. After the match, I saw him in Dome City (the equivalent of Sanctuary for PS players), and he was a level 31. I was level 9. Even with all his specialization, he was not invulnerable. That made me smile.
So far as how the weapons feel, the few I have tried feel pretty good. Additional weapons become available as you level a class, but none of the ones you start with are useless. In fact, I almost never upgraded a weapon in the time I played.
I can honestly say that I have no gameplay complaints so far. I'm quite sure that there will be balance issues - every MMO has them. I hope they have the capacity to handle all the action that will happen on launch day. I'm taking the day off.
My PC is a median speed quad-core with a 9600GT and 4GB of Ram. I know nothing about relative power amongst PC's, so do with that info what you like.
I hope that helps.