Every time I've bought vinyl tubing from the hardware store it's either been too stiff to use (thickwall) or the walls were so deformed from being rolled up that when you'd bend it it'd collapse (thinwall) so it too was unusable.
I've used it in the past. Usually the outer coils weren't bad too stiff, and you can buy 10 feet for a couple bucks, so that gives you 3-5 feet of good tubing. if you hang it up in a area that gets warm it helps straighten it out. My appartment had a closet with the water heater in it, that was perfect. The deforming is the biggest downside I see, but it can still make some turns in tighter space then is possible with thicker walled tubing. Also I theorize that at least initially, the area of the cross section of tubing remains the same, not restricting flow.