I finished Halo: Spartan Assault (bought it from the Flash sale last night). I thought it was a pretty decent twin stick shooter for the price.
I tried the weapons that you buy with XP points (or money in the case of the mobile version I guess). The rocket launcher is hilariously overpowered (150 round clip w/ no reloading required, and automatic fire). The sniper rifle is a one-hit on Elites, but other than that, it's not too OP. The other weapon, which I have not seen before since I've only played Halo 2, was fairly powerful (fires a high-damage beam that penetrates multiple targets), but has a somewhat long charge up time. In any case, I gave them one try each, just for the purpose of getting an achievements, but didn't feel any need to use them beyond that.
The control schemes both have some quirks. 360-mode has very noticeable auto-aim. KBM is really awkward for vehicles not surprisingly, and it apparently can't fire the plasma pistol's charge-up attack for some reason.
Missions are pretty short, maybe 5 mins each, and scoring is heavily dependent on multi-kills, kill chains, etc.
Overall, I liked it for what it was. Not sure if there's much I would have changed about this game specifically, but I wouldn't mind something similar, but with greater scope (longer, larger levels), like Renegade Ops. And some character progression persistence / RPG elements / perks / etc.
