Once being an advocate of bleeding edge, I have settled on 11.1.17(CA), which seems to be very stable. However, I am running 11.2.11P on two 4700's with HSSI's, which runs well (except for some unexplained frame-relay outages on one, which happens randomly).
We are runng 11.1.17(CA) well on 2501's, and 7206's.
We have to run the 11.2P series because of some particular VLAN bug fixes that have only been incorporated in 11.2 and 11.3. (Cisco wanted us to run 11.3.1 the day after it came out. I thanked them and said, "No." That image has since been withdrawn.) I am generally happy with 11.2.11P, but there is apparently a bug that causes f our RSP4 7513 to reload around 8 hours after a coldstart. (Fortunately, we don't power-cycle 7513s very often.) In general, I would recommend sticking with 11.1CA when possible. For one thing, it is the only version to support the VIP2-50 card. I have a brand-new VIP2-50 boxed up in a storage locker because I can't use it under 11.2P and Cisco says it will never be supported in either 11.2 or 11.3. When possible, I will probably back down one of our routers to 11.1CA so I can use the card. The 11.3 series does have some really nice features like HSRP for ISL VLANS, but I suspect it will be awhile before I try dropping that series on a production router. -dpm