10g RAC and defined services performance problem

We have a 3-node 10.2.0.3 RAC Server on Red Hat 4, and have defined about 20 additional services with preferred nodes set to 1 specific node, with available nodes set for the other 2 nodes. Workload is divided evenly with about 7 services on each node. Has anybody run into specific problems with performance when using a lot of services, as opposed to having the application just connect to the main db load-balanced service ?  

This particular application has a reputation from the developers of not scaling well across RAC nodes, and we have recently been advised of a lot of performance problems that I am now starting to investigate, but I want to get some opinions on the wisdom of using many different services rather than just a few or one.

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