I don't specifically use A2SD to do it, but I do have most of my apps moved to my SD card just via the Froyo feature. I would have to rate my Evo's performance as relatively instantaneous...I don't think it could get any faster and have me be able to keep up with it.
$40 is an "ouch" for me, personally. I've been buying memory cards for various electronics for like a dozen years now, and it's been a very long time since I paid $40 for a memory card (they were VERY expensive when they first came out -- I think I paid $30 for a 32MB -- yes megabyte, not gigabyte -- SD card). Lately I insist that the price be at around $1/GB, but that can be difficult with MicroSD cards since they're typically more pricey for longer.
It sounds like you made a wise decision and for good reasons. You definitely have a more future-proof 16GB card than I do, and I'm sure there will be more electronic devices in the immediate future that can take full advantage of Class 10 speeds, so you'll be loving life and I'll be hating it. Haha. Actually, I'll be buying a Class 10 16GB card for $16 by then, and looking at the price of the Class 20 and 30 cards for $80 and thinking, "OUCH!" Hahaha. Of course, then there will be no hardware to take advantage of Class 20 and 30 card speeds, but....I'm getting dizzy at this obvious circular pattern.