Issue RAM Caching with 11i Framework

You can use a profile to selectively enable/disable caching for certain paths. That way you can disable caching for paths containing per-user content, while still having the benefit of static object caching.

Alternatively you can use an iRule to get clever and can even fake the per-user behaviour by using Vary: User-Agent and rewrite the User-Agent in HTTP_REQUEST to contain user information, and then put it back in HTTP_RESPONSE.

RAM caching works fine - it's just needs to be configured correctly, and depending on your requirements, the configuration may be quite complex.