Just wondering if anyone has implemented siebel 7.7 with Oracle

We are currently upgrading our siebel 7.0.5 on Oracle 8.1.7 (Rule based Opt) to Siebel 7.7 with Oracle Based Opt).
We have made several tweaking of the init param basd on Siebel/Oracle's suggestions and overall for the Cost opt. The Application overall is performing good except for some exceptions where the screen hangs and or take much longer than the 7.0 environment. The UAT(User Acceptance Test) is over and some users have concern with this environment when they compare to the old 7.0 environmment. It is very hard to convince the management that this would be a ongoing tuning process which might take a little while to get every thing comparable. I have seen in few forums that people have been using rule based OPT still with the 7.7 Optimizer or atleast using the optimizer_features_enabled=8.1.7 since the 9.2.0 is having some issues. Please advise any issues you had to address during the implementation.

ANy advise will be helpfull.