I went from a 3 to a 4, sold my 3 to a friend (he got a good deal and I was happy to not have a hassle on eBay or Craigslist).
If someone gave me the 5 for the same price that I got a refurb 4 for, then I would take it. I like the 5, it's nice in the videos but the 3 was really kind of fine for me. I didn't want to take the overall hit in value so went with the 4. I'll do the same next year I suppose.
I'm locked in on a contract on my iPad line, so I pretty much had to stick to cellular and even in this cloud based world, I felt more comfy at 32GB, so I pretty much just spent a little stay more current for the next year and not depreciate my initial iPad purchase so much.