My first was the Moto Droid (1).
For my phones, it would be the Blackberry 7250 (my mom's), the LG Envy (1) , the Moto Droid (1), and in a few days, the Galaxy S3.
I think that sounds like a cool feature, but I see a problem with it because I know a lot of people who always turn their phone sideways(even when not in a browser or anything), and that would pose a problem for them.