I think it's alright. There's a crapload of sidequests (I mean dozens), but the main story is very short (maybe 8-10 quests). However, there's two new raid bosses, a bunch of new gun types (including Blue Text drawbacks as a parallel to Red Text bonuses), a new rarity (PINK!) that can only be bought with a special new currency, and a bunch of the series' trademark humor.
I'll actually say that the Season Pass would be a good idea, since it'll save you $10 in the long run, and if any DLC turns out to be crummy, you can think, "well, at least I didn't pay for this one".