So what is it? Well, it's basically from my brief experience, classic battlefield with a new mode. Tried out Blood rush which, yes, it's very similar to Payday.
There's an annoying weapon sway which seems to happen for no reason. It's also quite choppy performance wise. While I can run BF4 on ultra except MSAA turned down to 2 and get a solid 75-80 fps, here it's about 20-fps lower.
While I was recording the fps locked itself to 30fps with a few dips under here and there. Lightning effects are just as nice in BF4 but apart from that it's not really impressive if you ask me. Textures looks kinda low res at times.
Hit detection seemed at bit off as well, but I remembered to turn off network smoothing which helped a bit in my two games I played after this. Need to play a bit move obviously before you can give any real first impressions but it could certainly be fun with a few friends, but I think I'd rather prefer smaller maps with fewer players then.