I have a Xperia St15i with a 16Gb Class 4 card.
I searched the site for suggestions regarding a possible change of card in order to speed up apk's running, but what I found refers to other phones and other matters.
I wonder if switching to a Class 10 would make any difference. Anyway, I'm aware that internal memory size for St15i is obscene, and Link2sd could make things even worst.
Thanks for any hint.