I've used PEX for a bunch of purposes. and the rolled stuff can be used - I've used tons of it - but if you are making short pieces between fittings, its definitely not user friendly.
NO to the user four years ago who asked if you could use it for an automatic watering system because it doesn't burst when it freezes. Yes, that's true - but PEX is MUCH less UV stable than PVC. Recommend is that it not be exposed to sunlight for more than 30 days during install. I cringe every time I see a plumbing truck drive by with big rolls of the stuff hanging from their bed racks.
NO to the poster two years ago looking for PEX cups. Because its not long term UV stable. If you want "forever", get stainless steel watering cups.
To
@springvalley123 Yes, PEX is susceptible to thermal expansion and contraction. just like anything else. I use an estimate of 2 inches in pipe length change per 100 foot of PEX for every 10 degree change in water temp. Its about 20x more expansion/contraction than copper pipe, which is a bit over 1 inch per 100 degrees over 100 foot of pipe. PVC, btw, expands about 3 1/2" over 100 foot with a 100 degree temp change - so PEX expands about 6x more than PVC. For typical distances, the differences are immaterial.
For long runs, good planning can minimize the effects. For instance, i have a 150' run of 1" PEX from my well pump to my house. (Roll is good for that - there's only three fittings. One at each end, on at 100' where I installed a spigot). Because I buried it 3' underground (frost line 1") and because my well water is a pretty constant 68 degrees, I see no change in pipe length over the run because there's never any temperature change. The total run length from my on demand hot water heater to point of use is only 6 foot or so, so even though I have a seventy degree increase in temp, my total calculated pipe expansion is only 2" * 70/10 * 6/100 = 7/8". I can (and did) easily allow for that when I plumbed my walls. The things you learn when engineering your own house, right?
Because of the thermal expansion, particularly if you used the coiled PEX, I'd have the same concerns as
@Happily Retired re water-tightness, particularly if you had PEX lines exposed to full sun or a big water tank which could heat over time - those drill hole/screw in watering cups leak in all but the best of circumstances - attaching to a flexible, bendable pipe is asking for trouble.
Both Sharkbite and the copper primp rings can be removed (carefully) -there are tricks to both. I've used both types. The brass fittings can be reused, the copper crimp rings replaced. Sharkbite fittings should not be reused - but if its just a watering system for your birds, given that those things run from $13-$42 a fitting? I'd reuse it in a place I could easily access and hope. IF you used the correct tool to remove it. The sharkbites work like those "Chinese finger cuffs" - simply pulling the tube out damages (and likely destroys) the part of the fitting responsible for holding the pipe in a water tight seal unless you have the tool (or something like it) to force the mechanical attachment ring back towards the fitting while removing the pipe.
There's a third method of securing PEX I've not used- the UPONER system. I've not used it, and have only limited opinion regarding it (and that opinion has not been tested in reality) - but the start up costs ARE high. UPONER rings can be removed using a heat gun and a craft knife. Supposedly you can then install a new ring and call it a day, but I have some real concerns about repeatedly forcing PEX to mechanically expand, as well as with the application of a heat gun - they usually reach temps well in excess of PEX working temps. PEX begins to degrade over 180F - I've seen heat guns that go to 650F....
