I have yet to try an active preamp in my system. Anything between the original signal (vinyl groove, etc.) and the human ear has the potential to get in the way of the sound. Sometimes this is perceived as good and sometimes bad.
If it isn't there, it can't be bad; however, I may be missing out on something good.
Currently I have sufficient gain through a Quintet Black MC, a Rothwell MCL SUT, an EROS, a Submissive, and Paramounts through some Blumensteins.
I'm very pleased with the transparency and clarity of the sound.
I want to supplement with an active preamp like the BeePre to compliment the Paramounts. Money and available real estate to accommodate the Beepre holds me back for now.