Yeah, I found out about the one PS3 limitation last week when I tried to auto sync my home PS3. >8^/
Sony should fix this, but before that they should address the clock issue first. The auto-sync PS3s should be put on auto clock sync first. Right now, when my PS3 clock drifts too far from the server, the software will ask me to resync it to some Internet server manually.
Once they can guarantee a universal clock, then multiple PS3 sync should "just work". Just work.
EDIT: For PS+'s free content, I think you'll need to be patient. When the thing was first launched, our selection was zero and the early free games were meh too. Now I am quite happy to get "Plants vs Zombies" for free. Does the auto-update automatically download the free games for me ? I missed out on all of them except for PvZ.
The freebies benefit is not really for short term 3-month subscription though. The longer you subscribe, the more freebies you'll collect.
The discounts for "From Dust" and other games are nice -- after they implement discount for new games too.
I think they will have to fix the multiple Playstation sync when/before Vita launches. Otherwise, game resume between Vita and PS3 will be problematic. We should post to Shuhei's twitter account and press him for an answer. ;-)