We just completed our upgrade two weeks ago on our 8606, all 'E' modules with 8691's and 256MB RAM/16MB Flash/16MB PCMCIA.
No problems.
Our 8610 (The other side of the IST), running R and RS modules with 8692's w/MEZZ and in 'R' mode, also upgraded without incident.
I would like to note one oddity.
I run Java Device Manager in a Windows XP VM on my Windows 7 Pro laptop. It does not report the VLANID properly in the VRRP table. The VM is running the latest Java version. Running JDM under Windows 7 and Java 1.5.0.10 (Required for Kronos) has no such issues.
TankII