Windchill 10.0 can't be stable yet - not production released.
I installed it two times so far (PDMLink and ProjectLink) and spent about 6 hours sort of randomly looking at and trying things. I like 90% of what I see but there are some things that don't seem quite right and I need to take a close 2nd look at.
It will likely take some time to get the core PDMLink working, coming from 3.4 - tough to plan on having an ERP integration in place on day 1. Would be very worthwhile making the big jump asap for core functionality, and then a series of smaller jumps / enhancements / additions after. Going from 9.1 to 10.0 will be a much smaller effort than ILink 3.x to any Windchill. 10 has a VERY different look and feel vs. 9.1. Users will need some time to go from 9.1 to 10.0 if they start on 9.1, but I got used to it within a few hours.