I just picked the game up today, I'm in the same boat as you. I turned my settings as low as they go and I'm still experiencing FPS drops when in a firefight or when too much is happening. I'm using a Nvidia GEForce 765M. That was my biggest annoyance but I'm sure i'll be able to sort that out.
As for the gameplay. It was nice to finally jump back into renegade again and have it be so spot on to the way it used to be. I loved the new marksman class as well as the vehicles (mammoth and arty in particular). I did notice that the APC does literally no damage anymore to infantry. I held the thing on somebody standing still for 3 solid seconds before it kills them. In Renegade it used to just chop you down. The weapon ranges feel a lot shorter, especially with the volt auto rifle.
Is there a way to lock your vehicle yet? Because every time I step out to repair, it is stolen and kamakazied.
I'm pretty frustrated with the new Air strikes. They are literally constantly raining down. Is there a way to tell where they are called in advance like the ion cannon or nuke? Every minute these airstrikes wipe out all the engineers pushing or defending the tanks. I feel like this mechanic was implemented to break up those 20 minute long structure bashes, but I wish they were a little easier to avoid.
I love all the new characters and weapons. Great job so far, once I find a solution for my low FPS i'll be happy.