If you are satisfied with what you've already got, no reason to look elsewhere. Grass tends to be greener on the other side anyways. ^^ iPhone 4 is a great design (even more so than iPhone 5, IMO) and it ages really well.
Having said that, for someone who's contract is up and looking to get away from carrier leashes (i.e. me) Nexus 4 is just what doctor ordered.
I'm basically bailing on AT&T as soon as TMo gets 1900mhz HSPA up and running here in Charlotte. I'll eat the $280 ETF on my iPhone 5 line to save $100/mo.
I actually prefer the iPhone 3G/3GS design over the 4/4S's hard edges and lines. But definitely prefer it over the 5 at this point. Not to say the 5 feels bad, but it's way too thin. The plus side to this, IMO, is that now the phone is so small I can put a case on it, and it feels just right, as opposed to the 4/4S, which felt just about right and putting a case on it made it feel too big. I have a Otterbox Commuter on my 5 and I don't hate it nearly as much as I did when I used one on my iPhone 4.
As for shipping, yes, this shipping should be free. I guess you can look at it like the phone is already such an awesome deal, that they need to cover the shipping because they're probably not making it back on the phone, but when seemingly every other place that sells phones ships them to you overnight or next day for free, that extra $13.99 is kind of hard to swallow. Heck, I'd even prefer to see the phone priced at $325 and $375 with free shipping.