ZMT tubing is excellent choice. Especially for places where ease of maintenance is top priority. I have one working rig where case is externally abused on frequent basis. More scratches than all tigers put together.
There is also a lot of dust which is impossible to control - just using air compressor every couple months to blast everything out.
ZMT working like a charm. For bleeding/draining it's very easy. You can do really crazy bends with ZMT. Pricing is superb. It'll work a long time, not forever, but I guess 5+ years no problem provided that coolant is exchanged yearly. Of course tubing longevity will vary wildly depending on amount of heat put into the loop which is not the same with 1 Radeon 7950 and 4 Teslas for example or 1 i5 vs 2 Xeons.
Keep in mind that before using ZMT tubing flush it to remove possible rubberized residue. Fittings are very
tight (in confined spaces using tools may be required to un-/screw the compression ring properly) and unlike with PVC tubing you can't "adjust a bit" tube after screwing fittings if the bend or routing is not to your liking - rubber elasticity comes to play - tube will move back. Remember always wet heavily both the tube and barb - that way if you want to make some correction by few degrees tube will have some lubricity; if you fit it dry it'll be pain to move unless you have Hulk hands
. That's probably the only minus when compared to PVC.
I wholeheartedly support use of ZMT if looks is a non-issue. Fantastic stuff.