I've had the SFT for a few days now, although I need to give it a run through at some decent volume and so far I've only played it quietly through my amp or through headphones. Here is a quick review / comparison with the VT Bass...
I think I prefer the SFT to the VT when going for old school tones with a P-Bass and flats, where it's clean but fat and just on the verge of breakup. Great for playing 'Dazed and Confused' by Led Zep for example. It has more girth in the lower mids and seems to have a nicer 'feel' than the VT, the attack is less compressed so it sounds a bit punchier. Straight through headphones it sounds like it would be awesome as a clean recording preamp. However I prefer the VT for copping Geezer Butler tones that have a bit more clank going on (like War Pigs) since the SFT is rather mellow in the upper mids.
The SFT sounds very similar to a tube pedal like the EBS Valvedrive or DHA VT1 when cranking up to med/high gain, which isn't a sound I'm fond of as overdriven preamp tubes tend to sound thin and brittle when pushed past low gain. The VT sounds crunchier though, and when playing my Peavey T-40 with rounds for some Ric-like grind, the VT wins every time. Especially since I've discovered that a mild boost in front of the VT stop it from farting out on the low notes, even though it sounds counter intuitive.
At full gain, I can get a sound like the doom clip on Youtube with the SFT and a P-Bass. At the same settings on the T-40 it sounds plain awful, but it can be remedied by reducing the bass knob, so the sound you'll get out of this pedal very much depends on what bass you are using. To get the full gain out of it the bass eq has to be maxed out, since the SFT has it's EQ before the clipping section which I found strange. At high gain, increasing the bass knob gives you more overdrive and not much more low end. On the other hand, the VT has the EQ after the overdrive, so has masses of low end boost available - too much in fact, the EQ is really sensitive. The VT can get in the doom ballpark too, especially with a boost before it, but the more extreme speaker simulation makes it sound a bit more nasal. I need to put some rounds back on my P-Bass to see how these pedals react to that setup (I need a second P-Bass!).
I may do some clips when I get the time!