Someone on XDA mentioned a device wipe/reload as soon as you get it. I had mine for a few days and then wiped it and the lag seemed to noticibly decrease -- in fact, I can't recall getting any lag with screen switching since then.
I had considered exchanging this within 14 days for credit at Best Buy so I could pick up the Galaxy Tab 10.1, but decided to stay with the Acer. The SD expansion and USB port are extremely useful. I've used the USB port to completely charge my EVO in places I otherwise would not have had access to a power outlet.
I cant wait for the 3.1 update, the Android USB support announced at Google I/O should make that full USB slot very useful for a myriad of devices (external HD, keyboard, mouse, gaming, etc). I hope Acer is quick with the updates and I really didnt see anything, aside from the USB port, that would cause delays (no annoying manufacturer skin, etc). A little disappointed in the locked bootloader, but this is a really solid device, I only hope Acer doesn't let me down!