ArcGIS 10 REST API

It seems to me that the ArcGIS 10 REST API is good for -really- simple applications, but it's not something I would use in an enterprise application. Specially one that needs complex queries. Also, it has some problems and doesn't work correctly all the time. The latest problem I came up with is related to spatially querying joined tables. In my case, the spatial query didn't filter any records, it was like it wasn't even being run.

Of course, there's always the option of not using joins (and give up good database design). Not an option for me, so I'll check if there's a workaround.