In theory it's a great
In theory it's a great service. In practice I spent too much time waiting for to/from shipping and for the pedals I wanted to become available. The solution to these problems seemed simple to me: First, include a return label with the pedal, and ship the next one out as soon as you receive a tracking number for the previous pedal's return shipment. One order I could tell within a few minutes that the pedal wouldn't work for me. It took 2 weeks to get the next one because I had to wait for a label, wait for the return shipment. Wait for processing. Wait for the next shipment to arrive.
Second, pedal availability will always be constrained when you let users keep the pedals for as long as they want, and you only have a few of the high-end pedals that may be more desirable in a rental situation. I think most people sign up for Pedal Genie with the intention of testing a few specific items they are thinking of purchasing.
If you can't buy more inventory to satisfy demand, maybe tier pricing per week. So a default checkout time is 2 weeks, but you can pay a premium to keep your pedals for 3, 4, or however long you want.
Or maybe add a "get it now" premium option that lets you jump to the next spot in line for a pedal if there's a wait list. Keeping all that data from the customer may be wise, but for someone who is really hoping to use a particular pedal for a gig or recording project - not knowing what you're going to get or when is a frustrating part of the service. I cancelled because I found I could test a pedal by buying it and selling it at a loss in less time for less money (even paying for all shipping) than the PedalGenie subscription.