Freescan is completely free (with no registration needed, just download and enjoy). There is an option on the Freescan website to donate to the author if you choose to do so (I did), but the program never pesters you. Freescan is easy to use and can handle all your programming needs.
Butel's ARC-XT is good commercial programming software (I think it costs around $40, but they do have a free trial so you can try it first). It is a nice program and in some ways is a bit more refined, but I personally don't believe it does enough purchasing it when Freescan does everything I need. Many people do prefer it though so its worth giving it a try so you can decide for yourself.
ProScan is nice software and has some very nice features for remote monitoring, etc. If those features are something you would use then it is definitely worth a try (the free trial at least).
Happy Scanning