I think that the value of an alliance is greatly dependent on where you fly to most. Most of my business is between Asia and Central Europe and I find that Star is the only alliance that really works for me. I thought about trying to make Diamond with CX this year by using OW but it just does not work for me. However, if most of your business was in the UK or France/Benelux then I guess you might consider OW or Skyteam to be better.

Looking at the list of member airlines I would say that Star is quite a bit stronger than the two other main alliances and is certainly not falling apart.