I recommend it, in addition to some new features, a number of bugs got fixed. Some people like to wait a few weeks to make sure there's not some new problems that would affect them.
Why don't you read the release notes and decide for yourself:
The only drawback that we have detected up to now, is that the limance range is reduced when you make an output to mepg, applying the internal MC-Encoder.
Nobody knows why that happens, it makes no sense at all, the SoFo Codec avoided that in the past successfully.
:-(
4.b has driven me just about crazy. With 4.a I can record asio but not play back and play back Windows Classic Wave but not record. I go to 4.b and I can't do anything without major stuttering, buzzing etc.
Delta cards and drivers don't seem to be working out so well right now.
I'm back to 4.0 and using mostly 3.0c to complete important projects.