Anything that requires a potential penalty is going to make filing a tax return more frustrating, stressful, and difficult. It's just an extra piece of paperwork and another step to take in an already complex undertaking. Also, many people simply couldn't afford to purchase insurance and will undoubtedly find it difficult to prepare their tax returns because of the penalty.
I use an online tax service and I just answer questions. It didn't cause a bit of difficulty. I think the ACA is a worthwhile program because in the US, health care is outrageously expensive. The middle class and working poor people need all the help they can get. I don't resent the ACA one bit at tax time.
For me, simply answering two or three extra questions was not difficult. I recognize that it may be more of a hardship for those who had to pay the uninsured fee, but in my case and that of many others, the fee was waived because I couldn't afford insurance. All I had to do was tell them so. It was as easy as a few clicks. The minor inconvenience was easily outweighed by access to Medicaid, and even if it hadn't been, I didn't find it any extra hardship to do.
My health care company quickly sent me the appropriate paperwork required to file my taxes. I did my taxes with an online tax preparation company and they made it very easy to include the insurance form. I would estimate it added a maximum of five minutes to the time it took me to prepare my tax return.