I had over 100 items repaired under warranty before the 1st year was up. The key is to bring everything you notice to the dealer's attention and then make sure they get down to the root cause of the problem and don't just blow it off. Your slides sound like a problem and they should check them out. It could be a much bigger problem than just a slide adjustment. If you are going to do a lot of the repairs yourself once the 1 year warranty is over, then it probably doesn't pay to get an extended warranty as I've found most of them to cost $2,000+. I can replace my own hot water tank or electrical board for a few hundred dollars. I can replace my own fridge for $1,000. I can replace my own furnace. In other words, I'd have to have a lot of stuff go wrong for the warranty to pay off since I do my own work. Remember that many of your components have 2-3 year warranties and are covered anyway. The chassis should already be covered by Ford's 5 year/60000 mile warranty and that's the really expensive stuff - engine/transmission/etc.
If you don't do any of your own work and you're a worrying type of person, it's probably worth the expense.
Tim & Lisa
2011 Georgetown 350