We're arriving next thursday and planning to bring our own stroller, so this question was very relevent for me. I just called WDW-INFO and was told that the program is basically a 'pre-paid rental' with no discount. The first time you visit one of the theme parks during your stay, you prepay for the number of days you're staying and you get a 'voucher' which allows you to bypass the line and grab a stroller.
Doesn't sound like a very good deal to me. In fact, for people staying for long trips like us (10 days) it's actually a turn-off because there's no way I'm going to plunk down $150 (for a double stroller) just for the convenience of bypassing the payment line. I would consider it if the discount was substantial.
Of course, there's no way of knowing if the info I received is accurate. The CM I spoke with had nothing in front of him so he had to put me on hold and ask someone. Also, since it's a test, they could always modify it and perhaps add a discount, but I suspect they'd have to sell the LOS stroller passes at the resorts so they could tie them into your ressie (like UMPs).