My Halo 5 beta impressions thus far are: This is the logical next evolution in Halo and perhaps the best Halo multiplayer yet, as far as Team Slayer and the two available maps go. The game runs smooth, not many glitches and makes the Master Chief Collection looks even less polished than it already does.
My only real complaint is that the game is clearly way more geared towards hardcore / competitive players than a mixture. Matches were rarely very close. Either you win really easily, or you lose really badly. Most Halo games I've played in the past rarely have this many shutouts, and has a nice mix of close matches. It was extremely rare for this to happen.
Now that could be due to the beta just coming out and everyone being at the same rank, but I'm not so sure.
Some other observations: there is no lunge for melee at all, but there is a Spartan charge you can do if you are at a full sprint only. Shields only charge when you stop running. Boosting is REALLY fun and useful, a game changer alone. The controls take some time to get used to since sights are the left trigger. I hate the Xbox One's bumper buttons, they SUCK, as I've said since day one. There are only human weapons. Ground pound takes so long to charge up that it is really hard to pull off, and needs a direct hit for a kill. Both available maps are amazeballs and feel right at home.
Overall I'm very please with what I played and I can't wait for more of the beta to open up!
TL;DR: It is great, but maybe perhaps a bit too geared towards esports / competitive players.