Good thread, I agree with Don, I think that getting good information out there is important.
My experience's are likewise over many years (44 years shooting traditional and I avoided the compound completely). My friend Tim Cosgrove from Kustom King indicated that when their shaft was tapered it lost about 3-4 lbs. of spine on the overall arrow. Not a lot. I've mostly used cedar shafting over the years. I tried some forgewood shafts (not the originals by Sweetland) and when I took them out of the sealed plastic bag they looked like snakes. I've used the Ash shafts above as well as some pine shafts (I forgot the brand/type) and all were not easy to straighten, nor would they stay straight like cedar. I did notice that when my tapered cedars did need straightening, that more often than not, it was the tapered portion that was tweeked. Perhaps that's what Paul is aluding too with the competitive shooters shooting non-tapered shafting. I do believe that if you match the shaft to the bow (like with bareshafting method) that whether or not the shaft was tapered that it will shoot with the same accuracy. However, I guess if I were in a competition where a few points might make the difference in my placing, I'd probably want to shoot the most accurate shaft that was least likely to 'get out of tune'. I've certainly shot slightly bent wood arrows and hit the kill zone on a deer at 20 yards, but no way could you do that with a aluminum or carbon arrow (as Don mentions above with his tubular arrow comment). However, would I have instead hit the 'ten ring' had that wood arrow been without a bend?? That's probably what we're ultimately talking about here and perhaps why in competition those guys are using the parrallel???