I almost dismissed these products after hearing the demo of the Marshall - I thought it sounded toneless. But after hearing the Pete Thorn demo, I gotta say I'm impressed.
Evidently the Marshall demo guy actually chooses to set his amp up to have that generic tone (that you can easily create with any digital modeler or software).
It's funny, this whole modeling universe is a moving target.
I remember in the late 80s getting my first Kurzeil with the built in piano samples. It was incredible! No one had ever made a product with such lifelike piano sounds. I used it on a Budweiser spot, and the audio post engineer mixing the ad turned to me and said, "That's a great sounding piano, how'd you mic it?" And his jaw dropped when I said it was a Kurzweil sound. Now of course, it would sound absolutely primitive, compared to my 36 gig sampled Steinway sound. And I'm sure that in a few years, that, too, will sound primitive compared to the latest-greatest of whatever will be on the market.
I remember when the POD came out, people were nuts for it. My studio rat buddies and I all bought them. Very exciting, until we couldn't get the tracks to sit in a mix as well as going with a real amp...
So I guess my dilemma as always is, do I spend a grand on a load box/modeler or put the money into a great mic or mic preamp that will never go obsolete?