We gave it a few months and now have done several 9.1.4 systems; not too many issues. One thing to be very careful of if upgrading is if you are using any legacy cards or old licenses they may become invalid. For example a legacy VCM card with IP endpoint licenses... this is detailed in the release notes I believe though.
Another (little) bug I noticed is if you are recording AA menu prompt in embedded VM, if the user wants to re-record (don't they always want a second try?) you need to hang up and start over; the option to re-record during that same session will not save and it will always use the first recording.
crumthwacket - I haven't seen that on 9.1, although when we upgraded from 8.1 to 9.0 we lost voice path on trunk to trunk twinned calls (internal calls twinned to cellphones work) - I have a customer with 9.1.4 and the same SIP trunks and they don't have that issue.