Wanted to post these replies to my question before the issue gets too old...
ORIGINAL QUESTION So my question - does anyone have experience they're willing to share regarding Windchill 10... is it stable enough to get basic IL 3.4 functionality without worrying about all the bells and whistles?
REPLIES What is your deadline? No one will have production experience with Windchill 10.0. It is in pre-production now and anticipated to release (F000) in the spring (April). Actual release dates vary based on bug counts. The entire UI is a new layout, the SAP integration you desire has been changed and even basic Pro/INTRALINK functionality has been touched. I would be hesitant to install F000 into production. There is too much new functionality for it to be relatively bug free. Most companies won't even kick the tires until M010 (July) which means an implementation of M020 in October.
The "upgrade" from 3.4 to 9.1 is a migration, not an upgrade. While still involved, true upgrades (9.1 to 10.x) are much easier (shorter time and cost) than a migration. Like you I prefer to implement the point releases (9.1, 10.1, ...) but there was really nothing wrong with 9.0 M030 or later and it was a similar evolution over the previous release (new UI, new functionality, improved performance).
I would complete the 9.1 implementation now. A vetted system like 9.1 is worth much more than the promise of better SAP hooks. It is also going to be a while before the system is ready to integrate with SAP. Ask your PTC implementation team if they plan to back port the SAP integration improvements into 9.1 after 10.0 releases. You may be able to apply a future maintenance patch and get the hooks you desire.