Useful! I'm going to have to try it at Best Buy-- always hard to tell, though, with background noise. I did, with the IPT 5, though, bring my old iPhone 4 with me to compare.
The IP4 is quite rich and deep (well, for a little speaker) and trounced the IPT 5.
OTOH, I've come to realize that, unlike the iPads, I rarely listen to the IPT or iPhone straight up, so it may not matter at all!