you just can't have perfectly QA'ed stability at the cutting edge. Resources are ALWAYS limited (no matter what the price of the product is: 25.-, 250, 2500.-, that's only a factor of 100)), and then it's the question if you (or Nokia, or whoever) invests in improving quality from 99.9 to 99.99 %, or rather extends by adding something new.
And when you buy a 770, you can't expect it to be as robust as a 1950 analog telephone. But you can expect it to be more versatile.
Btw: I did not upgrade. I looked at the features, and decided I would not need them.