I don't see any problem with using bots as long as you are aware that it's not going to make you direct profit. I mean, you could get lucky and get a few % on your "investment" but more often than not the ROI will be in the minus.
If you are using bots as a promotional booster you can consider them as a long-term investment. And it is a legit way to get noticed.

Also to keep in mind people who are purist about Steemit and bots will be put off by bots busted posts.