mmm. ..interesting one. For reliablity I don't know if they have been around long enough. Having said that I have had quite a few niggly problems with my ZS180 in six months. Things sticking and rattling. Build quality on the ZS seems a little poor, particulary panel alignment. I've not really looked at the ZR's but build quality on the ZT seems much better.
I don't think you can beat the ZS for being the most fun to drive
KV6 is a suberb engine and probably best shows its potential in the ZS180, but remember to keep an eye on the oil level as they can be a little thirsty for the first 6-7,000 miles as some have found to their cost.
If we are talking build quality then the ZT is miles ahead of the other two, The ZR/ZS seem to suffer from niggly trim/cosmetic problems that considering they have been in production for quite some time should be sorted by now.
<remember to keep an eye on the oil level as they can be a little thirsty for the first 6-7,000 miles as some have found to their cost.>
I have done two oil changes myself and measured the old oil to check consumption and was suprise how little it used.
I too had been worried by low oil readings and it is MHO that most of the low oil problems we hear about are "ghost readings"due to bad dipstick design.
I would like to point out though, that i'm no engine expert and my opinions should be taken at face value.
I think the oil consumption very much depends on how the car is run in and what oil was in the engine in the first place.
As I understand it, from people like Roger Parker, If a fully synthetic oil is used too early in the engine life then this may not allow the pistion rings to bed in correctly leading to oil consumption. In addition if the car is not driven harder after the inital running in period this may mean the the piston rings take longer to bed in. My oil consuption leveled out at about 6,500 miles.
Yes you do have to be careful with reading on the silly black tipped dip stick. I leave mine over night in the garage and make sure that I get the tip really clean before I put it in! Lots of oil can sit in the top of the V6 engine for quite some time after stopping.
i did speak to roger at the classic car show and he did say he didn't recommend synthetics untill after 10.000.miles
i changed my oil half out of concern at oil readings and half at the abuse it gets.