That's only because you are used to modern crap over rated, underpowered SS amps marketed to guitarists. Trust me, if you spent 30 seconds playing my McIntosh 2100 solid state power amp, you wouldn't think it was in anyway lacking power or headroom compared to a 100w tube amp.
One of the claims I read about the IR-Load was that it had enough SS power to act like a 100w tube amp, which means if rated like the standard low grade Class D we are used to it would probably be speced much higher. It's interesting that they claimed the 50w Wampler pedal was 50 watts no matter the nominal impedance of the load and I infer that the 100w rating of the IR-Load will be the same. That in itself is pretty promising compared to current solutions that deliver 1/4 the power into 16 ohms vs 4!
The big question is the power supply. If designed right and there is enough juice behind it, there is no reason a SS amp can't deliver as much headroom as a PS 100. Well, no reasons other than cost size and weight, so we will have to see what tradeoffs they have chosen. My hope is that they didn't compromise in sound quality and power, and the price is still reasonable. It ain't gunna be cheap to deliver that, but hopefully not too far from the PS-2 and PS-100 range which is around $800 - $1200.