What an ignorant add. By that definition, we were all beta testers of every technology ever. Stuff improves and outdates current tech, that does not mean the previous product was an unfinished testing phase.
I own a WP7 (HTC HD7) and can say this unfinshed OS is not the work of beta testing phones. It lacks features which phones have had since...Well, ages, like being able to set your own ringtone, message tone, or whatever tone, and without use of some crap app.
Don't get me wrong, I love WP7 as a platform, but it doesn't exactly feel like the product of iOS and Android being a beta test. Whilst Nokia may have no control in that dept, it still makes up their phone they are claiming is the best thing since sliced bread.