My company is a Business part of ILog, we had integrated it with our transaction server. To many of our customers, business rules are very important asset, need to be maintained with great carefulness, they are not supposed to be altered by batch program. Actually I think Ilog has spent more effort than peers on tooling to make rule management/debug easier.
Though I do share with your concern about complexity and favor of BAL, I am not qualified to give you a definite answer. My work was plumbing between ILog and My transaction server, actually I use IRL(java like, which is more kind TRL) than BAL, as my interes is totally different than regular rule developers. for sure BAL is the most popular one and some company even customized/package it to make it more close to a specific industry. Our Insurance and telecom serive clients have lots of rules, maybe I should ask my collegues in professional serivice about their projects, i am also curious about it.
Why do you ask Ilog give you few reference accounts?