The Google AdSense has its own login account previously. During last year, it ask some people use their Google Account to replace the regular AdSense account login information.
But it is not successful, if your Google Account has already associated with an AdWords, AdSense, or Books account.
Now this limitation is broken. Google can provide this merge smoothly, even you has the Google Account with AdWords.
I have this situation. I tried to change AdSense login by Google Account, which is associated with an AdWords account. So it failed.
This morning, when I login the AdSense by my current AdSense account, it promot me to merge it with a Google Account. I still remembered the trial before. I think I can try it again.
After four or five steps, the convert is successful. I can use the same Google Account to access Google AdSense, Google AdWords, Google Analytics, Google Webmaster Center, and most important Gmail, etc.
Login once on my desktop, access all services from Google.
It is great and make life simple.
Google AdSense is one of best way to monetize your Blog. now to see how to make money on line.