These are great, and relatively affordable tubes. I got this as a spare for my bass head, but also have a few in my guitar head too, as they are great for getting the job done and sound great to me!
I haven't enough experience with different tubes to give a breakdown of the tone colouration of this tube, but it certainly made for an improvement over the stock tubes in both my bass amp (marshall-brand tubes) and guitar amp (JJs). They break up very nicely compared to both sets, but also provide more clean headroom.
Will probably continue keeping a few of these in stock, as they sound good, last well, and won't break the bank!