Different exadel.com customers uses big applications written in RF. Could tell you in general that the result especially using JSF/Seam/RichFaces and so on really depends on how good knowledge and understanding of the technologies do you have (valid for any frameworks I believe ). And talking about such projects I could tell according to my experience that some times after consultants review and related application changes - pages starting to work faster a few times. Just because initially was written carying about features only without good understanding what is lies under the hood and without any works related to optimization of those features but just using them as is by default.
To check simple sample of 4-5 times optimization for simple cases check great blog article by Dan Allen: