I have one that I used with my non-master volume Marshall. It was great if you kept it to -4 to -9 db. If you go to far it starts to sound fizzy. What amp are you going to use it with?
I have one that I use on my Vibro King and my Victoria and I think it works MUCH better than using a pedal (which is really the only other option in order to get a little dirt from these non master volume amps at reasonable volumes).
I have a LSS but I don't find the need for a hotplate with amps that have seperate gain controls.
At very low volumes, it does start to get "fizzy" but that's not what I use it for. I use it for playing in small bars at a tolerable volume but getting some of the dirt out of the amp.
I have one and it is great. It allows you to crank the power tubes and get them "pushed" while controlling volume levels. On the other hand, I don't use it much anymore. It pretty much is in a milk crate with a bunch of other effects and stuff which I have accumulated over the years.