PEX will be fine. Polybutylene, popular in the 1980s, has known problems.
PEX, with an O2 membrane, is the most common piping for in-floor radiant heating systems now.
Like most construction matters the majority of the problems relate to the installation quality, not the materials themselves.
As noted on another post, be generous with your bends and DON'T crimp the pipe.
There are several connection systems; the "shark bite" is probably the one in which one should have least confidence. If you are using a copper ring crimp system try to use non-metallic ells and tees (they have a lower failure rate), and use the "go/no-go" gauge on every connection after completing it.
It is impossible to tell which Chinese made valves are junk and which are good - they all look exactly the same. I use only North American manufactured components - you may have to hunt beyond you local Home Depot to source these.
Try to avoid pipe-to-pipe connections inside walls, especially runs from basement to upper storey; its better to use continuous runs for these.
The PEX system may be more tolerant than copper to Idaho winter freezing, but it's still not a good idea.
