I experienced improvement insofar as getting better at playing the games on the site. I experienced a subjective sense of some improved clarity of thinking. One example that comes to mind is that previously I was easily disoriented when out walking and taking more than a few turns around corners. My favorite game on the site was penguin race, a game that claimed to train spatial orientation, and I feel like this significantly improved my sense of direction when I went out walking places. I don't know whether this effect was real or has been preserved. I know that my skill at the game decreased slightly after a long absence, but that learning it again was faster the second time.

I got a two-year membership, and played it roughly daily for about six months. Not sure if I had any real benefits; my scores certainly improved on the games (overall BPI 96th percentile) but I was never able to tell if it really translated to any other domain. Take this neither as support nor condemnation; I just didn't really have a good measurement protocol other than Lumosity's own system, which is suspect for obvious reasons.

Also, the penguin game was really fun right up until the 200k point mark, at which point it became a chore.

I signed up for their yearly plan. I'm about three months in. I've enjoyed it, but haven't seen any signs of general improvement yet. My scores improved quickly early on, as I learned the games, but have been essentially flat for the last two months, even in the categories in which I really suck (40th percentile Speed, hell yeah).