Yeah, D2 does have a pretty good first impression. If someone is planning to play through it like a traditional campaign, either solo or co-op, you'll likely have a good time. For $4 and the goal of getting the basic story done, you're fine.
If you continue to play it, with the infinite grind that is how the game is designed to be played, you run out of stuff to do MUCH faster than D1. While subjective, the general consensus is that PVP is not as fun as the first game. Some of the big stuff you replay often has trash rewards and little incentive to replay, like Raids and the Nightfall, and much of the moment to moment loot excitement sucked out by the terrible Token based system. If the game is truly addicting to you, there is a good chance you'll run into the complaints many of us had eventually.
The reason people are STILL bitching now is just how poorly Bungie has handled the franchise. They bungled with D1 for over a year before really getting on track with The Taken King. They then did virtually the same thing with D2, seemingly learning nothing from the experience, and so far have taken 9 or so months to NOT fix many major and minor complaints. This slow turnaround time is amplifying everything, making Bungie seem to be stuck in the past, with fixes coming at rates you'd expect 10 years ago. It just looks bad when compared to the regular updates and content additions many other live games have, and their direct competitor Warframe makes Destiny look like a joke.
Regardless, $5 is a steal for a ton of quality gaming. Some people said not to even jump in at that price, but I'm glad I didn't listen. Even if I get fed up, I've already sank days into it and enjoyed it. Maybe not worth it at full price but for $5 vanilla or $20 with DLC, more than worth it and I'd recommend it to anyone. I almost didn't jump in at $5 because of these sort of comments.