How do you get them?
The currency is legendary shards, but don't worry - you will be swimming in them. Even casual play will net you an abundance of legendary shards, and Xur's rates are very cheap.
I have held back for the PC version but my 2 friends capitulated and have played the PS4 version. I think they said there were into their 3rd play-through with rank 28 and 29.
General summary was 'good' but not 'great' game and similar problems to D1 i.e. grindfest with not enough content however, when human team members are in the mix with you it is a much better experience.
Yes of course two nerds on their third playthrough after just a couple of weeks will complain about a lack of content.