APC is the most straight-forward solution, IMHO. However, you should not confuse opcode caches with cache drivers holding user content. Most opcode caches feature that too, but it’s not the same
If you’re looking for a super fast solution: Try if you get lucky with memcached. It’s entirely memory-based (which also means all the cached content will be lost if the server restarts).
Your decision does/should depend on the traffic you expect and the scale of your architecture. For most websites (arguably the vast majority - especially on shared hosting environments) you will have no problem using CFileCache. CFileCache does have the added benefit of being easy to work with and since it stores .bin files in the filesystem (/protected/runtime/cache/) you can add your enhancements to work with cached files, timeouts, etc.