I used to do that every year. It wasn't hard. However one year I forgot to copy line 12b from form 9876 to line 34c of form 5432 and when the IRS caught that I had a big mess to clean up (since state taxes copy federal taxes so I had to refile state with the corrected numbers...). Now I just pay a small fee to FreeTaxUSA (I figure they deserve some money for their efforts in creating software).

One thing I can say for sure: doing taxes with a computer takes me longer than filling out the paper forms by hand! There are so many delays while "calculated" (as if a ghz computer can't add numbers fast), and loading question pages that I can obviously skip (I never worked for the rail road, I'm not blind...) but take extra time because of how they setup the UI.