I have stayed at Pop more times than I care to count. I would say that paying a few extra bucks for preferred room is well worth it, usually it puts you in the 60's building right by the pool. After a long day at the parks that loooong walk back to your room in the 50's, 80's, or 90's buildings is sheer torture. Don't get me started on taking that walk multiple times after spending all day at the parks to fill your resort mug, get a meal, etc...
Its ultimately your call on whether its worth it, but take into account that what doesn't seem that bad on a normal day will be magnified 10 fold after walking/standing for 5-6 hours straight in the Florida heat.