The core bits mostly work fine, including running the app pool in the IIS7 default Integrated Pipeline mode. However, that's where it stops. I've had plenty of trouble with third party modules in my main portal system.

Anything that has an http module or other web.config addition should be seen as suspicious when things go wrong. I've also had one module out of action for 2 months due to the pathetic license activation garbage totally killing the whole system. That took some tracking down. Turned out that it doesn't work in the 64 bit environment. Also turns out that I think the developer made a serious and highly unprofessional error in judgement.

Several other modules have also failed, but generally without killing the system. There are also RSS issues with some modules.

I'm getting off track.. but as you can see there are migration issues. Setting up 4.90 from scratch is much easier. Do that first, then migrate.

Rob