In regard to employee retention.... it depends upon the employee's attitude, but I'd say it's a net win for the shop.
We've been doing the tool allowance for the last 6 years. New guys, especially young guys can be a little funny. We try to hire people in their early 20's (Gen X-ers) which means it's inherently impossible for them to see the big picture. Things like KPI's, profitability and efficiency are not even on their radar much less what it truly takes to build on a career and self-reliance. We try to teach and mentor them on every aspect of not only our business but their career as well. Taking a young man and opening his eyes to the monumental scope of our business is no small chore. Nor is opening his eyes to forward-thinking the scope of his career and his life in general.
If a guy can be observant, see the big picture and make it past the first year, then they start getting a little hungry for that allowance and want to see the 2nd year through. By the time the 2nd year is up they should be taking more notice of how well the rest of the shop is kept equipped, how bonuses are paid out when we surpass our sales goals and how they can improve their situation at the shop through their own initiative.
We pay hourly at our shop and work as a team. On days where there is more work than a man can say grace over, the best suspension man does suspension work, the best AC man does AC work, the best diagnostics man diagnoses. On days where there is not enough work to go around, the best diagnostics man or the best AC man or the best suspension man will teach what he is doing to anyone with an interest in bettering himself (and we notice who is trying to better themself and who isn't). Also, nothing is below any man's pay-grade. If I need one of my L1's to do an oil change because my B-techs are hoofing brakes and ball joints, then the L1 does the oil change.... and an L1 level PMA.
Where the teamwork pays off is at BONUS time. Through the years we have deduced what annual sales figure we need to achieve to cover all expenses and make a nominal profit. Once we've achieved that goal, each team member receives a 3%-5% bonus for every dollar in sales beyond that number.
We also pay for ASE Tests and give pay raises for successful passage of the tests. The mechanic needs to take the initiative to study and schedule their tests, but they can ensure a yearly raise if they take an interest in becoming a professional, well-rounded mechanic.
On the other hand, if a new hire turns out to be your average booger-picking, mouth-breather.... they're not observant, cannot see the big picture or is generally unmotivated he's not going to last long. Unfortunately, there is no avoiding these people. They can ace the interview, talk a big game about how they want to learn, be enamored with the goings-on for the first few months and then totally implode. We've had guys quit after 1 year and we've had guys quit after 1 day.... lol. This is after we've invested a few thousand dollars into bringing them on board and giving them every tool they need to succeed (not just physical tools in this case but training, mentoring, etc). Even in those cases, we're glad to see them go, we pick up our tools to help the rest of the crew with the workload and go back on the lookout for the next potential winner.
So, facts of life.... turnover is going to happen, 1 out of 3 hires is going to be a long-term hand, not everyone is going to get your program and appreciate it. We believe our hiring process, our willingness to help our guys be better mechanics, our work hours and our compensation plan are superior to just about anything the competition has to offer and by that standard we don't get our feelings hurt when a guy moves on because we just move on too.