Chris,
I've tested several different laptops (and their AC power supplies, all of which are switching power supplies) and they all seem to generate the same kind of broadband noise that is the worse between roughly 5-8 MHz but affects higher frequencies, going up into low VHF band, messing with 11 meters pretty badly. Local receive on 27 MHz is totally obliterated when my laptop is connected to the same AC circuit as the radio's power supply (Astron RS-20A). Putting RF chokes in the DC line for the CB/11 meter radios and HF equipment helps a little bit, but doesn't eliminate the problem. I find that connecting the switching supply to a different AC mains power plug reduces but doesn't eliminate the noise, especially when comparing noise levels to a "clean" DC power source (12 volt car battery - direct connection). These tests were only done using 27 MHz CB equipment, as I don't have a proper HF mobile setup, but I imagine they apply for most of the HF band.
I've noticed that its not just switching power supplies used with laptops, but switching supplies in general. One particularly terrible offender is the cheap switching supply that ships with the Radio-Tone RT-SRC1+ simplex repeater controller. I swapped one out for an older-generation RadioShack AC-DC converter and the difference is crazy. The Radio-Tone switching supply adds 7-9 S-units of noise to the noise floor on 11 meters / 27 MHz.