ok this is how i stand
my ps3 has pretty much been a GT5/6 machine
i have a few other driving games like Supercar Challenge but thats it
i'm interested in Wipeout Fury but I might find something fun with the 'instant game collection'
chances are i wont get an xbox one any time soon but a ps4 isnt out of the question
i dont play multiplayer at all, should get PSN+? I hear its only $30 a year? no?
i also only have slim 160Gb - would i need a bigger drive?
A couple of other bonuses are that games seem to come out earlier in the US, you don't have to deal with Australia's rating system, and the games in general are cheaper (although the AUD is dropping). I know those bonuses aren't specifically linked to PS+, but they are definitely factors worth considering when setting up an account.
Something else to consider; If you have no intention of playing online (ever), you can still make purchases and download ICG games from your US PSN/PS+ and play them on your AU/EU PSN (and vice versa), however ensure that you're on the corresponding region's account when buying DLC, as US DLC is not compatible with AU/EU content (and vice versa)
I've personally got a level 13/14 AU/EU account, have been subscribed to the AU/EU PS+ service for ~16 months with prepaid subscription until early 2015, and I am heavily considering dropping it for the US service, mainly due to the above mentioned factors.
You'll definitely get more than you pay for out of your subscription, especially if you have multiple devices, and you can 'purchase' for consoles you don't have through the webstore, allowing you to maximise your gain from the subscription.
12 months of PS+ on the US PSN has been $30 a few times (and you can save the code for one of those extra 3 month events to effectively get 15 months) whereas PS+ on the AU/EU PSN rarely has sales.
People say the US PS+ has more sales but the AU/EU PS+ has better IGC games.
I'd go for the US PS+ purely for the price. IGC games eventually go to both so it's just a matter of time.
Edit- And to answer your question: Yes, get it, how the hell don't you have it already!?