I had a little bit of time this weekend to download the F# CTP. The IDE portion of the CTP is a huge improvement over the previous CTP. In particular the intellisense engine feels much more smooth, is available in new places and has much better results. Project engine also has better integration. Debugging support is much better.
Overall the IDE now really feels like a ... well IDE. I felt like the previous CTP was forced into Visual Studio and had much more in common with the old C++ IDE than VB and C#. This time around the IDE is just more smooth and more closely resembles other managed integrations. Definately worth the upgrade.