If anyone with the HX model also has the M9 or M13, I'd be interested to hear about the difference in sound quality of the effects, please.
After playing with the HX over the weekend, I will say the old effects are still very usable and sound great. I stacked the Octo and Particle verbs in a single foot switch and they definitely held their own compared to the newer verbs like Glitz. Note that the new stuff are considered stereo effects, whereas the legacy ones are mono (at least for the reverbs). That being said, the stereo effects eat up more DSP, so you can run out of power if you use too much of the new stuff.