i have not used Gunbot or any of the other bots out there, i have my own so i can not make comment on their software but from what i can see the problem with these people selling their software is that they bought it only because of false advertisement.
if you look at these bots, they have an affiliation program which you can get paid if you refer someone to buy it. so the internet was filled with spams of lots of idiots advertising these bots as magic where you just click a button and the profits start pouring into your pocket. so desperate newbies who didn't know what trading was started buying it and then while using the bot they not only couldn't make money but also lost a lot so they are now trying to make some of it back.
as i have always said, a bot is only a help to a trader that is already making profit at all times with every market status. if you can't do it already then a bot is not going to change that for you.