Playing games to train your brain?

I've never been much of a (computer) game player. Oh I've played my fair share of RPG, MUD, strategy games etc. when I first started dabbling on computers in my teens, but managed to wean off in my early 20s when i realized how addictive they were. (Plus I discovered boys or something.)

Couple days ago I stumbled upon Lumosity (www.lumosity.com), a website filled with games that supposedly can help improve cognitive abilities such as memory, attention and speed. I definitely sense a constant decline in my cognitive abilities during my 30s, so the site piqued my interest. After just these short 2-3 days of playing the online games (each of them are quick to complete and difficulty level increases the more you play) I do notice that I respond faster and remember things a bit more (at least while playing the games, not sure if it translate to real life yet). And my BPI - Brain Performance Index - has increased, at least according to Lumosity.

All is well and good, right? Having some fun and possibly helping my brain to stay in shape. And with each game being short and quick (unlike most other computer games), I can play/practice as little or as much in each session, depending on my schedule and interest/mood. So what's the catch? Well, Lumosity is subscription based. I'm currently using the free trial right now which will expire in 3 days. So now I'm wondering whether I should subscribe to continue playing or just forget it? Will it be actually effective? Will I get tired of the games? (not so far but it's only been a couple of days... although they do add new games from time to time). Will I get the same results from playing regular computer games instead?

Does anyone have experience with Lumosity or similar sites/apps? Did it work for you? I'm looking for something that's fun yet not too addictive, AND can slow down the aging of my brain. Lumosity seems to have the potential, but I'd like to hear some opinions and thoughts before I invest...