I've set up a few of these for clients who have already been persuaded by their brokers, but only for 1-3 employees at a time. I would avoid setting them up for anywhere close to 150 employees.
There are some open issues, but to my knowledge they have never been a high priority for enforcement. The biggest open issue in my view is whether these plans are:
(1) annual bonus plans not subject to ERISA at all
(2) ERISA welfare benefit plans in which the company is helping the employee buy life insurance
(3) ERISA pension plans
If you don't have any restrictions, i.e., company pays premiums each year and employee can do whatever he/she wants with the policy, I think you fall closer to (1) or possibly (2). The more "retirement-like" restrictions you add, e.g., restrictions lapse only upon termination of employment following age 65 or 10 years of service, the more likely you are to fall under category (3). Retirement-based restrictions on 150 employees starts to look an awful lot like category (3).
If they are pension plans, and paying into the policy makes them "funded," they violate a number of ERISA requirements. I've never seen an official pronouncement on their status, but the insurance marketing materials always include a disclaimer saying "talk to your tax and legal advisers to ensure you are not creating an ERISA pension plan, etc." That risk will always be inherent in the REBA plan design, but they are sold nonetheless.
With regard to vesting, the materials I've seen label the process as "vesting" but are really gradually reduced repayment obligations if you leave prematurely. The company also won't be able to deduct any premiums if the company's repayment right can be enforced against the policy (and arguably if the repayment obligation is based on the cash value of the policy).
If you can stomach the risk, they are useful plan designs.