I got it in June this year in preparation for the PS4 and I have to say, I'm really happy with it (even if I barely play online...)
At first, I just used it sparingly. The cloud saves and auto trophy updates were nice, but not really essential and not really worth any money since the PS4 does it automatically, but in the last few months I've used it a lot more
The PS3 games were generally old retail games that I already had, or weren't interested in (unfortunately DMC has come post-PS4 and that is one that I do want) and since you can't use retail saves, it's not like they're useful at all. The same was also true for most of the Vita games, I already had Gravity Rush and Uncharted. But recently, that's changed massively
Obviously, the big one is Resogun and that alone was worth about half the price of the subscription, but I've also enjoyed Guacamelle and actually taken advantage of the savings on offer. I also have a few other games stored up on my Vita now I'm done with the (also free) Jak Vita trilogy.
I guess I wouldn't play the likes of Contrast or Don't Starve if there were more PS4 games (or they had harder trophies) since both are terrible. But it's hard to argue with the value that PS+ does provide even if you keep buying many retail games at launch
