I've used OpenTaxSolver for years & have found it extremely valuable. Bugs seem rare, yet quickly addressed when found. The command line interface all I use, as it's quite straightforward and easy: give it a datafile on the command line, and it generates an output file with the lines to fill in on the paper form. It's easy to make a tarball that contains not only the software, but my datafiles; this is invaluable when filing an ammended return. It might be nice to automatically store as a datafile the standard output from the runs, as that's where most worksheet info goes. To date I've done that with tee: taxsolve_US_1040_2008 2008_US1040.dat | tee 2008_US1040.wrksht . The only other improvement I could hope for is a crystal ball that takes into account year-to-date earnings & withholding from my current paystub. It would have to assume last year's tax rules (or perhaps a reasonable projection), so it seems logical that I'd be running the 2008 software in crystal mode throughout most of 2009. Actually, that's exactly what I've been doing, but having OpenTaxSolver do the math on the paystub would be nice. A couple examples showing how I use it this way: 1) am I on-track to owe a small amount, or am I withholding too much? 2) how much can I gain from stock sales before the AMT kicks in (& significantly increases how much I owe)?