Oo, very useful article! I recently bought a CafePress t-shirt for my girlfriend and while it turned out ok, the price and available colors weren't quite what I would have liked. It was an organic shirt, so it's going to be more expensive, but I ended up paying upwards of $30 for a printed (front and back) t-shirt, and that seemed pretty steep. I see pricing is possibly a bit cheaper with Printfection, *and* they have more color options for organic shirts. Very cool. The print quality of the CafePress shirt is also mediocre, so I'm intrigued by this person's review of Printfection being much better. Of course CafePress offers some products that Printfection does not, but if the product is available there, they do seem like an interesting option.
Overall I think I'd say use CafePress only if they're the sole option that provides the product you want to make. Otherwise use Printfection (based only on this person's comments for now) if they have the product you want. Use Zazzle for any large prints, e.g. posters, etc. as that's really what they specialize in. Use Kodak or someone similar for photo prints and photo books (or maybe Lulu.com).