I strongly recommend this software for calculating and submitting taxes. If you are using a competitor's software package, I would suggest trying it one year just to see.
I've used H&R Block tax software for years. It has always been easy to use and produced accurate results, both federal and state. In addition to the usual annual tax filing, the section to prepare an amended return is also very easy to use should the need arise.
Pros: Easy to prepare, Easy to import documents, Fast