Lastly, I would like to report bugs, the animation after a while turns into complete polygons, which frankly looked quite funny. I see polygons moves around, and doing things.

That thing happens on pretty much all titles every once in a while, or at least all the ones I tried. Interestingly it only happens if multithread + dual core mode is enabled. When pcsx2 runs in single core mode, its much more stable (but slower).

 

I believe the project is focused on overall compatibility and not not specific speed.
The more important thing is that as one problem is resolved in one game, an issue (most likely to be speed) might as well appear in another game.
Nevertheless, you can say it is buggy by judging on a specific game. Consider that A LOT of games went from nothing or 5fps to full blast (KH2!!!) and that REALLY BUGGY to smooth and savable (Tales of the Abyss!!!)

Compatibility>>>optimization (Also, compatibility often yields speed, but speed almost never yields compatibility)

 

If I remember correctly, some members or developers mentioned that if you are not getting 100% on both cores this means your system isn't using the dual core correctly (You might need updating drivers or some windows fixes.) or your video card is limiting you, it's too slow to allow 100% processor speed.

 

What more likely is that your graphic setting is too high (ie AA*16 or something) and that your GFX is bottlenecking your CPU