I've got it enabled on this forum. The benefits will vary depending on the application. The thing to remember is that each time data is commited to the table, the cache for that table is flushed. So for read-only tables, the benefit is huge.
In the case of this forum, there's probably a 50% hit ratio overall. This seems pretty poor, but it's a little misleading as most of the tables enjoy a 90+% hit ratio. The session table is constantly updated and that drags the overall hit ratio down.
All you can do is try it. It's unlikely that many applications will see a performance decrease with it enabled.