Our debate over trees also throws in "how fresh is it" and "how sturdy are the branches," but that's part of the additional complication of using real candles on your trees. Aside from that, it's more a matter of "how even are the gaps" than "how straight is it" for our family.

Also, a wonderful alternative to tinsel which has the additional benefit of being reusable and traditional is to go for tin icicles.

http://www.google.com/search?q=tin+icicles&hl=en&prmd=ivs&source=univ&tbs=shop:1&tbo=u&ei=W6f7TEOEvJUH-d2EjAU&sa=X&oi=product_result_group&ct=title&resnum=1&sqi=2&ved=0CCsQrQQwAA&biw=1024&bih=547