Before locating my current (new to me GW1500 with CSC) ride, I looked at Tow-Pac, Voyager and Trigg for conversion on my '07 Yamaha Roadstar.
I really liked the Trigg the best for me, but that is simply an opinion as I have never ridden one. I did ride a Kawasaki with a voyager, and really saw no problem with it.
With the value of my Yamie and the cost of any of these choices I would have had within $3K invested, of what the '95 GW cost me. With this I gained more comfort, stability, cruise, stereo, cb, air shocks and trunk space. The '95 actually had fewer miles than my Yamie, so I felt it was 3K well spent. But I about wore out a computer for 3 months looking at every bike and trike for sale within 1500 miles.
If you really, really love your current ride, then these kits are a viable alternative to a full conversion kit due to the big price difference. It is really an individual thing, and I know a lot of happy riders on bikes that don't interest me. They probably wouldn't be completely happy with my choice.