I'm playing on default setting (haven't changed them) and my fps goes from 100 to 35-40 at times. I think this has something to do with looking at river. Fps drops aren't that common and I can barely feel them.
With standard launcher I'm playing on lowest possible setting in DX9 mode, and my fps is usually around 60 most of the time and game feels sluggish.
With this beta launcher I'm able to keep browser open, play in windowed mode at higher settings and with rare fps drops. Game feels a lot faster, like I'm flying but that probably has something to do with increased FOV I have set (max FOV).
For me these occasional fps drops are quite normal, considering graphical settings and my old machine with only 2 GB RAM.