Yeah, I've +1'd quite a bit and integrated it in to my blogs.

I'll bet Google detects +1 manipulation from users with the same IP that tend to +1 the same sites though. I'm reasonably sure that aged Google accounts would also carry more authority.

Maybe it's because I'm in Mexico, but... I have not even seen it. Still I'm somewhat interested in how it will affect SEO.

I may be asking a lot but, if you notice any positive effect on your rankings, would you mind sharing the info? It would be really appreciated.