Got to 15 on my first try. Would likely have done better with a touchscreen; it's much harder with a mouse. Ultimately, it was the introduction of locked-together blocks underneath other blocks that killed me, and in particular the fact that blocks you already had "loose" can suddenly get locked to other blocks.
The Android version is a ton easier to play, but I feel there is something lost when trying to see the whole field of play on a tiny screen. I'll try it on my Nexus 10 and see if that's any better.
I agree wholeheartedly with the other comments: this is a awesome game and well executed!
Small nit: on Android apps, traditionally pressing the back button when at the "home" or top-most screen of your app will either exit, or prompt to exit.
It was also extremely not obvious how to disable the sound; traditionally I would have expected that to live under the "More ... " item at the home screen.
I hope these are taken merely as suggestions, and not as criticism.
