We hired a tax guy in 2012 and 2013. I always did our taxes prior to that and this year, becoming more Mustachian and less willing to pay for convenience, I didn't want to pay $200 to the accountant. Plus our taxes are less complicated than 2013 because we are no longer paying a nanny as a household employee. Plus I'd already seen a couple of instances where the accountant made mistakes that ended up counting against me.
So when reviewing our federal taxes, I found an error on last year's taxes that I'd have to refile in order to get our money back, and when preparing the corrected forms, I found another omission. Total savings $350 for tax year 2013. So I figure I saved potentially $900--$350 for 2013, $350 for 2014 in preventing the same two errors from happening again, which they likely would have since they pertained to the mishandling or non-handling of situations that were similar in both years, and $200 on a tax preparation fee (which wasn't deductible because we didn't meet the threshold). And a few bucks on gas to drive to and from the accountant's. Not bad for a few hours of work.
My takehome from this is that while the accountant knows tax law better than me, I know my own situation better than anyone else, and while he gets paid no matter what, I do better if I take advantage of every deduction due to me--thus making me better qualified to look at each potential deduction and figure out if it applies to me or should apply to me. And honestly I've never found it THAT complicated to figure out tax forms/rules as they apply in my own fairly simple situation (mortgage, student loan interest, 529 plans, kids, and now "self-employment" with no expenses again).