Generally very good if you are operating within its limits - which most people do. Last year I did hit a difficult situation due to too many stock transactions than the software could handle - but most people will not hit it.
The software works and has met my needs. I found what appeared to me to be an error in the results once. I find much of the help text to not be very helpful. I usually have to go to the IRS documents if I need to figure something out. I keep using it because I'm used to it and don't know that another product would be any better
Most mistakes I have ever experienced. Taxes needed to be paid kept increasing even after removing some information. Program seemed to add rather than subtract items from memory. I finally paid a large amount of tax only to find out, using another program, how much the final numbers were off. Then had to complete a 1040X by mail to correct the over payment. Which still has not been verified by the IRS.