For a shelf atop a steam radiator, absolutely (plastic melts; metal and glass conduct too much heat; the radiators [since they're heated by steam] get hot enough to burn flesh but not to ignite wood).
For a dowel in a curtain, not at all.
For an air conditioner prop, depends on its weather resistance properties and whether it's open at the ends (don't really want to make it a home for critters). In this case the plan was to use the aforementioned screw gun to attach the 2x4 to a piece of 2x6 that I already have -- which is a lot easier to do with wood than metal if you don't have specialized tools.
1) doesn't sell standard sizes (already tried that one last year); also, relatively fancy and expensive woods compared to the cheap pine I was hoping to find
2) won't cut to custom size; mostly already-finished
3) ditto
4) discussion... mostly about buying in larger quantities, presumably from people who have full garage/basement/backyard carpentry facilities in which to cut it to size, etc.
For a dowel in a curtain, not at all.
For an air conditioner prop, depends on its weather resistance properties and whether it's open at the ends (don't really want to make it a home for critters). In this case the plan was to use the aforementioned screw gun to attach the 2x4 to a piece of 2x6 that I already have -- which is a lot easier to do with wood than metal if you don't have specialized tools.