I've been following BB10 very closely and following the SDK's they have released. I've taken a look at them just for fun. I don't program anymore but if I did I would be happy with everything RIM has been providing to make things run smoothly. I've also been following blogs and what other developers have been saying about it. Here are two positive articles when it comes to developing for BB10. Also let's not forget the other articles that have been posted here on crackberry stating how easy it is to port your existing app to BB10 in its native language.
With all that being said, I think RIM is on the right path to success with developers atleast. Now RIM needs to get the interest on the consumer ens which I feel is going to be a challenge.
The BB10 on dev alpha is not the best build. It's buggy and the UI is choppy at times. At other times, the UI's fine. It's supposed to be working better on the dev alpha B and for sure RIM internal builds are much better (like the one on display at BB10 Jam and used for the demo).
Its a beta version, it will get better. Even though it was choppy at times, its not enough to really complain about it. But RIM needs to work out the kinks before the launch. Can't be like apple maps, RIM needs to be successful from day one!