I feel like I should get a copy of this manual as it seems to be the bible for this sort of work and while I imagine that I can find most of it's information scattered about the web I'd like to have one place where I look when I have questions about machine setups. Is there any major differences between the 27th edition and the 28th edition? I can find the 27th for about $50 cheaper than I can find the 28th.