yes, have considered it, but from first enquiries it seems they are charging rates that are simply impossible to fund at this point, well in the tens of thousands of dollars. I might be able to bring the rates in line with incoming revenue, but this one's a very scary approach, not being vc funded.
also, gnip doesn't seem to have actual real-time access to follow/unfollow events and only access to 1/10th of the public tweet stream, offering a 'sample' of all tweets (which is what the non-whitelisted accounts also have).
you do realize that sample 10% nonsense is simply untrue if you have a way to get the stream for the X,000,000 most popular accounts on a daily basis right (it has to be because getting streams for a specific account has to have all the tweets, not 10% of them)? Forget the bots, just focus on the active users.