If it's in the sun, it will be very hot to your skin, since the top of it is thin-metal.. It's actually not that hot at all if its in a regular temp evironment (80 degrees or so), it's about 60 celcius. Which isn't that hot, considering it doesn't have a fan. XM's SKYFi runs just as hot, except they use enclosed plastic casing on it... So the heat is not felt by holding your hand around it.
The AudioVox SRS uses plastic casing too, so it doesn't FEEL as hot.