First of all, really cool game, looks fantastic, great environment.
After I lifetime of playing FPS including the first Insurgency I would suggest the following:

The voices from the first game were really spot on, in Insurgency 2 they lack the same depth and are a bit censored compared to the first game.

I miss the 'F&^K is he ok' or 'Stop shooting me you 'f%^&ken idiot' the more natural way that soldiers talk with each other. This voice actor I have experienced is a bit too 'official' sounding where soldiers are generally talking more to each other like in the first game with slangs and having a dig at each other. I realise it may be too late for this being the beta 2 and all but it takes away from the authentic feel that the original game had. Also the insurgent side has the same problem, the voices were way better for both sides in the first game.

The sounds from the mortars are great (the firing) however the impact sounds are not realistic at all, if you have a look at a youtube video of incoming mortars you will find they have a distinctive whistle whilst they are dropping before impact.

There seems to be some kind of screen flickering issue I have experienced with the latest Nvidia drivers on my GTX1060 when walking through smoke from smoke nades.

When you're waiting to get into a round you don't have enough time to choose a loadout. Maybe if you use custom loadouts but if you want to quickly change loadout there is simply not enough time. I took about 35 seconds and then I couldn't spawn because the game had already started and I had to wait until my team captured a point. There was no audio cue or anything to let people know that the round was about to start.

I will add some more feedback as I play a bit more but that's what I have thus far.