I've had one of these for a few months now. For me it's the best Tech 21 preamp yet, very hard to get a bad sound out of it and VERY versatile. As I've probably mentioned in this thread before I'm not a fan of Harris' flatwound typewriter tone at all so it's definitely not one for just the Maiden fans!
I've tried lots of Tech 21 preamps over the years - the Leeds has always been my go-to, I did use the Dug for years but that has a very distinct character that was always there. The VTs never worked for me.
I think the XB Driver could topple the SH in terms of the tone I'm after but honestly I doubt I'll ever get to try one thanks to the diabolical pricing over here.