We purchased a very lightly used (7k miles) '18 KA 3 months ago. Not sure about the engine changes between the 17 and 18 KA, but I love the 605. It is actually more fuel efficient than the 600 I had in my '16 Cornerstone.
The 17 KA's had some problems with the digital dash, which was fixed, usually, by replacing the computer. Not really sure what the process was, but the previous owner had to replace the computer on ours as well. We have not had any problems with this. The hydraulic pump for the HWH system and heater core seem to be common problems with these year models. Our hydraulic pump failed, but was replaced free of charge by HWH. No problems since. We did have to replace the passenger side heater core (the KA has separate heater cores for passesnger and driver), but this was done via my extended warranty.
The positives are multiple. The fit and finish of this coach are night and day to anything Entegra offers. The ammenities are endless. This is one of the few coaches out there with an inverter dedicated to running the midhsip AC with the battery bank. We never need the genny going down the road. The ride is very quiet, much more that my '16 Cornerstone, and the KA just feels like a tank. Super solid. The little details on the inside are all very well thought out, and the decor is very much to my wife's liking (she never quite liked the decor in the CS, but I loved the K3). Now we are both happy.
I woud say a well taken care of '17 KA is a good buy. Just be careful with the above mentioned issues.
Fred and Cindy, CA
2008 Marathon XLVII, 2018 Raptor (towed)