So far it's slower. I need more practice, but I think in the end it'll be best to use it like 50% of the time.
Some sequences just aren't good for PAO, and sometimes it'll be too similar to another image you had earlier in the cube or the multi.
That's cool. Collective letter-pair images list is an old idea and this is probably the best implementation so far.
Also, just about time to mention this: http://bestsiteever.ru/letterpairs/