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 just saw a commercial for Lumosity, which is a mental-skills training website. It seems like something that someone on LessWrong would have tried, but some googling of the site turns up only some passing mentions. Has anyone actually signed up and used it? Have you had results, and are they worth the subscription cost? (~$5-15/month, depending on subscription length).