I used to do my taxes, but when I once worked a lot of different jobs in the 80's one time, I wanted to make sure I wasn't making any mistakes.
When he got done with my return, I ended up getting nearly all my withholding back, and owed a lot less on the jobs where I didn't have withholding. Had I tried to do this myself, I would have lost about $3,000, a HELL of a lot of money back when I was in my early 20's.
The tax guy I used says that EZ forms are really there to prevent people from determining their actual bill, which in nearly every case is significantly less than using the EZ return scales. He did my taxes the next 20 years, and saw zero audits. Each time he did it, it was significantly lower than my own estimation if I did it myself.
Of course, I got lucky and used someone who knew his shit, which of course is key. One can run into a total dunce or even crook and really screw the pooch, but just do a little bit extra work and you'd be amazed at how much you can keep away your hard earned sweat from Obama and (Socialist) Company.