Sorry for the delay, I've not been having time to test new plugins.
I downloaded newest develop version and I'm gonna test it now, I'd like to make some questions to better understand how all these caching are done.
1) I noticed "object cache" is implemented together will all other caches, it seems each kind of cache is an interface and calls another instance which is what effectively caches data. So, "object cache" isn't fully new implemented right? it's using cache implementations that are already used in 0.8?
2) Where is W3TC_LIB_W3_DIR defined? I see it being used but can't find what's it.
3) I also can't find where caches are being stored in HD. It seems you md5 group and key and I have no idea where it goes.
4) What does database cache do? As I understood it, you extend original wpdb class, and caches all queries results, then when the same query is requested you get it from cache instead of accessing database, is that correct?
But is it reliable? I believe "object cache" exists exactly so that developers can avoid database queries when previous queries are cached and they believe data hadn't changed. If you do the same thing in database-access layer, creating 2 layers of caching, isn't there the risk of changed data being ignored and taking away from developers the capacity to control when cache can and can't be used?
I also noticed something annoying. If I delete wp-content files, they are gone forever. To force them being copied again I must deactivate and reactivate the plugin, but doing so I lose its settings. I suggest adding an option to delete all files and recreate them, for situations when they may need some fix. And another option to reset options, removing the reset from deactivation hook.
In overall, Total Cache's "object cache" seems to be a bit faster than File Cache and much better maintained. I'll keep testing and probably use it when a stable version comes out :)