I'm pretty happy with the tones I'm getting from my POD HD500. I am picky about how I set my tones up on it.Some of the guitar players here swear by adding a compressor to the front end of the pod. My model already has a compressor in it though.
I don't have one or two favorite tones, so sometimes the POD works well and other times it might be something else. I have never went overly crazy about my tones . Maybe I'm too easily satisfied with what I get, but I am a tweaker. There are a lot of settings in the average POD type box. If you factor in the signal levels and what you play it into there are a lot of variables. Two guys could have the same exact POD and be getting different tones from the same setting.
Others have mentioned that "fizz" sound at the top end. I don't hear it in my POD.
I think it's fun to record something and add plug-ins to the signal or copy tracks and comp them. I might have a POD track and then add Guitar Rig to it or a one of the CLA guitar plug-ins. Depending on what it is or what type of sound I'm after. I recently read about Alice in Chains latest album and their guitar tracks having 15 tracks...5 panned left, 5 panned right and 5 in the middle all different amps....from one guitar. This is nothing new, although phasing is an issue if not dealt with.
But the "fizz" you mention isn't something I have had...unless I don't hear it :) I like my POD a lot.