I've been a big fan of this series since B1.
I got to play a few hours of couch co-op today and I quite enjoyed it. I'm reading a lot about how it's just the same old Borderlands but imo the game felt markedly improved. The gunplay was WAY better and the movement changes (particularly sliding - this game does sliding much, much better than Destiny 2) make the fights seem fast and more chaotic in a way that is different from B1 and B2. The new classes (that we played ie Moze and Flak) were really fun and different from any previous classes, making it feel fresh.
Graphically it looks fantastic.
We did run into the same lag issue that's being reported for couch co-op. Whenever either of us opened our Echo menu the game suffered big lag for both players. This was annoying but not game breaking, as we just coordinated to stop and go through loot during safe/down time. It is pretty unforgivable to have this issue in the final build of a AAA game that touts couch co-op though. Hopefully it's fixed right away.
It definitely is Borderlands and they've stuck to a lot of what's made this game appealing in the past, however imo it's s gross misstatement to say that it's just a fancier looking B2. In the same way that a game like Titanfall 2 improved on the core of the Titanfall 1 experience but kept it a game about fighting in big mechs, B3 sticks to what's worked and makes a lot of QL and gameplay improvements in other areas.
From what I've played so far I'd give it an 8/10.