I've been talking to Howie about this piece of kit and he has recently installed one on his BI SERK.
Has anyone else had any long term experience with this and if so do you think it is a worthwhile addition or not. The principles behind the True-Track appear sound enough, but is it worth the $ ?

Nige
Many here have installed either the True Track or Ride Str8 devices and have had them on for quite some time. Competing products with similar effect really.
There's not been one universal response. Some have noticed immediate and significantly positive gain. Some have found "a little help" from the devices. And some saw no real difference at all.
The odd man out to all that is that the "problems" and the reasons for installation were not all the same to begin with. So it's tough to make a fair comparison.
In my own case I'd never experienced the dramatic "rear steer" shake that others had. I had, however, had a very repeatable rear end based oscillation that would present in longer sweeping turns if one were travelling at certain (potentially citationable) speeds or greater. The device installed on the back of my bike made that better.
It, of course, had no effect on handling issues in the front end that stemmed from turbulent wind coming up under the fairing and just shaking the hell out things. That silly little 20 dollar wind dam did more to help that than anything. Learning when in/around semi trucks this was going to happen made a difference too.
In my own case I knew going in that the device in the rear was at least partly prophylactic. Some of the "problems" seemed to present over time. The device should help stabilize the rear and, therefore, slow down down wear and tear in the bushings. It will, in other words, help keep things better longer. Of course we can't know how much we're helping there. At least not until it doesn't seem to break prematurely and we convince ourselves we did a good thing. But between losing the rear oscillation and this potential gain I'm still satisfied with having done the install.