I don't know if I have been hanging out with the IRS too long or I've acclimated myself to government forms, but I just completed my taxes in about 1 hour and 15 minutes, including gathering up all the supporting documents. More surprisingly, I found the entire process very easy in spite of the complications of now having business income (Requiring Schedule C-EZ) and filing married separately.
For the past 6-7 years, Mohammed and I had HR Block do our taxes because Mohammed was an immigrant and a student, so there were always complications with fellowships and stuff. So this year was the first time that I had to use the IRS 1040 form.pdf in a long time. It was really simple to use (mostly because I don't have all those crazy deductions and credits that make it complicated). Yet, there were also cool aspects of the design that made it easy to follow.
For example, the Adjusted Gross Income section was indented so that if you had them, you can do the calculations without confusing you when you get to the total. If you did not have Adjusted Gross Income, you could skip the entire section until the last row in which you could place the out-dented total adjusted income.
Or how in the Tax and Credit Section or Payment Sections, the really complicated calculations are indented, with the final totals out-dented.
Other usable design elements were the listing of which additional forms to attach and where one should place data from those forms, such as the Schedule C for business income or Form 3903 for moving expenses.
So it becomes an interesting problem that it is not the design of the IRS forms that make paying taxes complicated, but rather the tax laws and itemization and credits that make it complicated. I could imagine a situation in which you have several additional forms to complete for different line items. Yet, the 1040 Form is not complicated in and of itself. But again, I've been hanging out with the IRS a long time, perhaps I've drunken the Kool-Aid.