[billmcintosh]

I'd recommend 2 things:

Send out a reminder email to everyone and remind them they registered to your site and give them some news about how the next version is coming out. Also let them know that as a registered user you will be emailing them from time to time.

Then a few days later send the promotional email.

This should help avoid anyone getting upset and making spam claims. That is your biggest problem: that you will upset your users and they'll report you as a spammer even though you're not.

I'd recommend you look at related affiliate programs instead of AdSense though. I'd imagine payouts in the gaming market on AdSense will be quite low. Good targeted affiliate programs should make you more money.