I think the biggest MBCBP concern was addressed when the plan was conditionally approved as optional. Trapping compensation in the MBCBP that pilots would otherwise prefer to spend or invest elsewhere is worrisome. This is further compounded by the potential that self-inflicted 401k excess funds could be forced into the MBCBP. IIRC this was addressed last year when the MBCBP proposal was limited to 401k excess on earnings above the IRS limit, not self-inflicted 401k excess via after tax 401a contributions. There is concern about the unknown. Pilots who exercise the most control over their finances seem to be the ones most concerned, while the set it and forget it crowd seems generally in favor of it.