I've always carried any amp I've had with me. Velcroed to my ipod. Guess an old school like me who lugged a discman around while walking or biking finds a small amp and an ipod little bother. Doesn't even feel heavy on my belt to me...well worth the so called hassle.
Yes I carry it everywhere, is it worth carrying along with me? No and yes, it makes my ipod sound listenable, but it still an ipod and it is a pain to put it in my pocket, and take it out to change songs.
Used to carry various Xin amps for years but has downscaled to just the iPhone now. No doubt the amped sound was better but in the end I could not be bothered so convenience won. Anyway I find that the sq advantage of the amp deminishes a great deal if the environment gets noisy as public transport tends to be. Now for the rig I set up in the hotel room when I travel I would never do without an amp.