The first time I went worked out great. The manager was there servicing the payment machine and he gave me a mini tutorial with helpful tips (e.g., if you get the package that includes the undercarriage wash, drive slowly or you'll miss it). It was about $10 for a wash and wax and the windows and body were left surprisingly streak-free. They have vacuums you can use for the interior.
My only complaint is that the second time I went the machine wouldn't accept any kind of payment. I tried paper money, toonies and a credit card to no avail, yet the machine didn't indicate it was out of order.