I think they can work, just as doing puzzles and things as a kid stretches you too. A friend of mine asked for wordsearch puzzles from me (I layout a newstand wordsearch magazine) for just this reason after watching her dad with Alzheimers. I think the software can be good but is definitely over-hyped for a paranoid market.
But personally I think it’s better to have a life-long brain workout. We know from kids that there are important stages in life where certain types of knowledge are more easily absorbed (particularly language) so start early and keep with it. I’m a puzzle addict, having subscribed to Games magazine since about 13 (I still have it shipped over to England) and when I’m feeling bored I go do another degree. Haha!

I’ve been using the site Lumosity.com for about 8 months and I have noticed a major improvement in my cognitive processing ability as well as my memory and attention.  I think they may still have a free 2 week trial -  Check it out!

@ Tina - I’m afraid that if I start doing puzzles/games I’ll never quit… they’re that addicting to me… I agree about the lifelong brain workout. We’re trying to instill that in our kids (5,3,1) at an early age so that they are pre-disposed toward curiosity.

@ Cary - thanks for the tip about Luminosity.com. I’ll check it out!