I think PSN+ has allways been great value, but games and discounts has gotten much better the later years. Personally, I've allways made profit in savings on discounts alone. :-/
The first year it were probably worth thinking on how many PSN-games you usually download, we got much more of those back in the day - but you still got some big stuff like originial Infamous, LBP, and Wipeout HD, I think. :-/
But after the first year, they really stepped up their game alot thanks to some member-polls, reintroducing monthly free games into Instant Game Collection - making the later years a
no-brainer, unless you don't have internet access with normal download-speeds, and don't have to pay for your games yourself.
Just downloaded Spec Ops the line, and Far Cry 3, not sure what I'm going to play first.