Check out this presentation by Justine Jordan (Litmus) and Jay Jhun (Engauge):
There's also a UK version:
Eloqua's chart of the week shows the impact of subject line personalization on open rates:
The graphs shows that subject lines that include a name have open rates about 4.7% over the average.
Does that mean you should go ahead and start including your recipient's name in your subject lines? Maybe.
Just make sure to test this with your audience to see if it has a positive effect. I remember us testing this when I was still running eBay's email campaigns and we found that in some countries it increased our open rates, while in other countries it decreased open rates. So test, test, and retest. If you see that it has a positive effect on open rates, then roll out with it and retest regularly.
The biggest positive impact on open rates comes clearly from making your subject lines timely and relevant to your recipients.