I used a different preamp pedal that was essentially the same thing (preamp section of an amp in a pedal, complete with tubes and all that). It sounded awesome and I loved the tone, but what I didn't like was the principle of it, in my mind an amp is one thing and a pedal is another so it just felt strange, I ended up selling it. It sounded great, it sounded just like the amp I wanted, going into the power section of another amp it was fucking awesome tone, but in my head I had that weirdness and I didn't want to stay with it (mainly cuz I couldn't justify the $450 price tag or whatever it cost me, for a pedal that;s already doing what my amps did). I actually see these as being more at home in a live rig where you can have your tone dialed into your pedalboard and plug into whatever amp is at the gig.
Do you remember which one you had?
I've actually separated out my preamp and power amp sections for a while now so if a preamp is on my pedalboard or mounted in a rack, there is no difference conceptually. I'd just rather not carry around a 45lb guitar amp head just to use its preamp (which is what I'm doing currently). I'm already using a Mesa 20/20 as a power amp.