I switched from CPT/KPT after having been with them for 30 years but having been in legal conflict with them for over 18 months. During the conflict they turned up to be arrogant, treated me with contempt and any questions they couldn't answer or which showed them to be incorrect ended up in a black hole. With my "protection juridique" I finally got what I wanted, but they then upped the premiums by 14% at the end of last year (it wasn't just me, everyone in the canton got the hike) and I decided that there was no way that even the cheapest health insurance could be any worse than they were.
I moved to Assura, saving myself some 70 CHF per month in the process. Really the only complaint I have is that they're slow in reimbursing bills. CPT/KPT used rarely to take more than 2 weeks, whilst Assura seems to spread out reimbursments and they can take up to 6 weeks (apparently, though I haven't checked this, they are legally supposed to take no more 4 weeks).