as mentioned by a pp, on an empty bus, strollers aren't a big deal. On a crowded bus, forget it, it is downright miserable.
when we use WDW transportation,we rent a stroller at the parks (however, that was before the price hike!). when having a rental car, we bring our own.
when using WDW transportation, we keep a stroller at the resort. this is to use from the room down to the bus stop, we check it in at guest services in the morning and pick it up when returning at night. this allows us to stroll the little ones from the bus stop to the room at night when they are usually asleep.
last year we rented a minivan (got a smokin' deal, $295 for 14 days) and brought a double stroller that we got off of craigslist for cheap, then split the cost with a fellow DIS'r. We also split the cost of a fridge with the same DIS'r. Staying at value resorts means no fridge unless you rent one. Renting one would have been more than buying one for our 14 day trip. Renting a stroller for 14 days, well forget that too. We had a double jogging stroller and a fridge for 14 days, total cost out of pocket was $80. We also saved on drinks and food by having a rental car and shopping offsite. So for our 14 day trip, the savings on the stroller, fridge and food more than made up for the car rental. We had free
DDP but like to have cereal for breakfast in our room, saving meal points for lunches and dinners. we also brought our own bottled spring water so we could use our snack points for treats and not drinks.