My rear tire on my Giant Escape needs replacing but the front tire is fine. Is there a problem with putting a different type of tire on the back than is on the front? The front has the original tires that came on the bike. They are Giant S-X2 700X32 puncture protection. I am thinking of putting an Armadillo tire on the rear.

Try it, Its No BFD.. But your newest tire should go on the front,
because front Blowouts cause Crashes and Injuries because your control is Gone.

I decided to replace both tires with Specialized Crossroad Armadillos. I have the same tires on my Cypress and they have held up very well.

You can save money by replacing tires one at a time, but rears wear out faster and fronts are more important as mentioned above. So, its best to buy a new front tire and move the old front to the rear.

Or get a new pair

How many folks use a bigger tire on the rear for more comfort? I just bought a set of 35c Mondials for my Traverse but was thinking about going with a 40 on the rear. I'm about 80/20 pavement of some kind/hard pack trails.

I saw someone riding with a set up just like that today! Does it help much?

I frequently do. My hybrid has a Rubino 25 on the front, and a Specialized Turbo 26 (which is really measures out to a 28) in the back. A couple of my road bikes have 23s in front and 25s in the back. I also prefer a more supple tire in the front and a more flat-resistant tire in the back, even if they're the same size.