I am really waiting to try the VT.
I normally get my sound via the bass and the amplifier and don't use any effects except a occcasional chorus or octaver when required. I bought the Tech 21 Programmable Bass Driver DI ("PBDDI") recently while on the road because I was blown away how good it made a passive Jazz bass sound into a monitor amp. Couldn't wait the extra month for the cheaper VT.
The up side is that you can get some very convincing tube sounds out the PBDDI.
The downside is that if you use active electronics, you have to disable or adjust the signal stength to that of a passive pick-up. Otherwise, the effect sounds very cheesy. I am guessing this probably explains while the results from readers who have tried the PBDDI have varied all over the map.
I now run my active bass outputs to an old Boss DE Delay rack with adjustable output and the delay effect bypassed. This allows me to dial in the correct signal strength to the box, then twiddle with the level and drive settings. It is an iterative process. With some fiddling, I can get some very convincing tube emulation sounds that are exactly what I want. All I really want is a SVT, a B-15 ("flip top") and rarely, something heavier and brassier that sounds like Flea on Blood Sex Sugar Magik. I find it helpful to start with the bass tone and boost controls at neutral.