I used bots heavily for awhile. Put all my rewards back into bots and rolled for a couple of weeks. My experience was mixed. By bidding late, and only picking bots in the money, and spreading my money over several bots. I stayed a little positive but not much. Lots of work for questionable return. The other side about bots being counter to the spirit of Steemit, I agree with but I don't begrudge those who choose to use bots. They are choosing their experience. I don't think it is as rich as developing friends within the community but to each their own.
The thing is ... when you hit the trending page you are more likely to find some of those friends quicker. It speeds your accounts growth. Plus when the post you promoted with a bid bot gets noticed by a steemian sometimes they visit your blog and upvote other post as well. So your return isn't only on that one article / post.
As you pointed out its allot of work to make sure you are coming close to breaking even with bot use. I know for a fact I am not but all my SBD is generated from my posts and winning contest.
I think the key for long term success on Steemit is growing your account with a handful of others and visiting each others blog and upvoting and supporting each other as you all grow. Once all accounts involved grow to the point of each upvote being worth something thats when all the previous hard work pays off.