Ah yes, very true - I do recall the whole fun and games with 3! I wonder if Ofcom will proceed along the same route with O2/Apple..
I think this is where things will get interesting, as if Ofcom do step in andforce O2/Apple to to carrier unlock their phones, essentially they'll open a massive legacy iPhone market (we've already seen some fun and games on eBay for imports or unlocked models), especially if the iPhone is fully unlocked from the manufacturer.
I can imagine a lot of people wanting a slightly older model with the full features, however It could also get messy as I can also see Apple refusing to repair or warranty the iPhone after the 18month window (and being out of contract) so it could end up being a risky approach for the consumer...
Unlocking the iPhone in my experience is actually scarily easy nowadays (I know a number of people who've had this done), you wouldnt be entitled to free upgrades
and invalidate the warranty on the thing, but at least have a wider choice of providers. Again it's interesting that Apple's decisions in firmware upgrades differ from the other phone manufacturers (and the established expectations), Nokia for example won't dissalow a firmware upgrade to it's handsets just because you dont use a partner network.
Building network specific 'value added' features like Visual Voicemail in my opinion is where the networks could really gain, as this is something that would be a sales point for the network and not the phone itself - even though the iPhone may be the only (current) device that supports it!