Technically, I submitted a total of 213 since the beginning of the year to get 41 approved (not counting some new ones that haven't been approved/rejected yet). That gives me an official 19.2% success rate. However, that is quite misleading as I did a little experimenting with BB to see what they accept. I intentionally submitted some lower quality ones and some keyword based ones in order to get a feel for what they accept. None of them were complete junk - I didn't want to clog the pipeline, I just wanted to better understand their thinking process - but I also wasn't expecting them all to be accepted. If I went simply by the ones I expected to be good enough, we would be looking at probably a 30-35% success rate at least. Honestly, some of my prize domains were rejected (and I'm okay with that)... and I've already sold a few of the ones rejected for $xxx each.
Hope this helps!