Having no FPS issues as I'm playing on a brand new PC, but I can completely identify with the other main caveat / issue being the UI.
The maps have been overdone, are too detailed and make it difficult to pick out friends or quest objectives amongst everything else. On the other hand the text for everything from chat to quest trackers to tooltips seems underdone - I play unmodified WoW in the same resolution with the general UI scale the same, yet everything is so easily visible and/or accessed.
If Carbine don't fix it before launch I'm hoping there'll be addons out pretty soon that do. Everything else about this game is so slick and polished, but arguably the most important visual element of an MMO is the UI.