I'm moving from the 1.2 API to the 2.0 API but still using 9.3.1 map resources. In a test app, I can't get IdentifyTask to return results (if it returns at all) on these map services in the 2.0 API. I copied the sample app for IdentifyTask from the new (2.0) API sample page. The app works when pointed to the original map url, but doesn't work when pointed to my maps. Other apps using SL 3 and the 1.2 api referencing 9.3.1 maps don't have this problem (I haven't yet tried moving my sample app to SL3 and API 1.2). I checked the map urls and they do show Identify as a supported operation.
I'm experiencing this in two different apps with two different maps (on two different servers). In fact, even QueryTask doesn't work when given a map point, but attribute queries do work. So there seems to be something involved in the spatial query aspect.
Has anyone else noticed this kind of behavior?