Guess I really did open a can of worms with this subject. :-/ I knew everyone would probably have differing opinions and that is fine provided no one is rude to each other and so far that has been the case.
You do bring up some good points Tsarfan and Dasha.
I really think that this question can't be answered with 100% accuracy as can any of the other "what if" questions. No one really knows what kind of Tsar Alexei II would have been because sadly he never got a chance to rule.
There are several situations that I think could have occurred had Nicholas II died a natural death and Alexei become Tsar.
He could have become a weak Tsar just like his father and let his mother and Rasputin rule the country.
He could have become the best Tsar Russia had ever seen bringing about major reforms and turning the absolute monarchy into the greatest constitutonal monarchy the world had ever seen.
He could have become another Ivan Grozny and delighted in torturing in exiling people who dared to question his authority.
Or he could have become a good Tsar, better than his father but still not considered great. He would have moved Russia toward a more constitutional form of government but still not as much as like in England. (this is what would have happened IMO) I think he was mature enough to have realized and learned from the many mistakes his father had made.
And I agree with IA. Speculation is fun!