Buying the game will grant you full access to its content, without a subscription fee. The only real paywall are the free-to-play esque items that you can buy from the in-game shop, which aren't really required, and are mostly cosmetic.
As I've said many times before, I enjoy jumping back into Guild Wars 2 sporadically, as I don't have to worry about a fee if I just want to check out a new patch or play a few rounds of PVP. In that regard, it's a pretty easy sell to people who are already MMO fans.
Guild Wars 2 [ArenaNet]
ArenaNet to hold a public beta for Guild Wars 2: Heart of Thorns' Stronghold mode
8:00 AM on 04.09.2015
Guild Wars 2 is getting a streaming client soon, getting you into the game faster
10:00 AM on 03.05.2015
ArenaNet: Guild Wars 2: Heart of Thorns 'is like Metroid and Zelda slammed together'
8:01 AM on 03.03.2015