I think it's a great service that allows you to try 100's of games for 1-hour risk free and not have to repeat the "demo" portion if you opt to buy any of those games.
It provides you great discounts that both reduce your cost and highlight specific PSN or PS3 titles.
Access to early Beta's haven't been too good a value. Beta's usually harm games for me because I over play a game that still has problems and then don't care when the full release comes (with exception of Uncharted 3 which I bought even more enthusiastically after the free-beta thing which convinced me Uncharted multiplayer is a good component of the game where I previously only cared for single player). On the flip side, hopefully the data they collect and any forum feedback they receive help them have a stronger game at launch.
The full PS3/PSN games being free is a great way to provide the last version of game leading up to sequel coming out. It ends up working out in favor of good game franchises and would work against poor franchises. So far the main value of PS+ is perceived to be here and that value is driven a lot by Sony PS+ team ability to have some really high profile quality titles and best of PSN as well. These aren't 4 year old games nobody wants to play. Giving Walking Dead Episode 1 & 2 was a great entry for many to the series that would have otherwise ignored it. Some other games that review well but sell poorly are also good treats that the PS+ team seems to target for the free section. It was always quality and now increasingly quality+quantity and also the all important diversity (not all shooters for instance).
