After researching various technologies available for water treatment (specifically the removal of minerals) I further researched company websites and Homestars. I chose two from Homestars, one with high ratings, though pricy, and Water Depot whose shop was quite near my home.
To make a long story short, I was more impressed with the in-home quote performed by Home Depot - Andy took the time to explain the local water issues and was at pains not to oversell anything, and also warned of a few things people in the industry will try to sell you, either by a lack of knowledge of the local water or just trying to make an extra buck. He struck me as a friendly neighbour. I even sauntered into the shop one day and asked to take home some treated water to compare against our own, and they were happy to help.
Contrast that with the other company who doubtless does great work but whose attitude (as I took from the in-home quote) was "yeah we're great, we're on HGTV ya know, and anyway I highly recommend the top end system here and as for how it works etc it's all online." Further, when I did research more RO solutions by the manufacturer they use, the lady on the phone had no idea what I was talking about, though did eventually get me a quote.
So to sum up, Water Depot sold me a system based on a strong gut feel and the fact they were at every stage happy to help answer questions and concerns, versus a hurried and vaguely arrogant feel from the other company.
The system works perfectly so far (3 weeks). Couldn't be happier.