I'll put my 3G on kijiji too. Checked it out this morning and a jailbreak 16g 3g goes for 250-300$. The only problem for me is not having a phone for a week!
Have an iP4...Got it in the UK.... and it's Great. It's faster than 3GS, and the visuals are as good as mentioned in the inital announcement.
With regards to the whole Antennea issue.... I haven't experienced any problems either in UK, or here while visiting. (I do have a case for it.... as I don't want it scratched after reading/seeing pics of such).
With regards to the phone being unlocked.... if it's like the UK... Unlocked means exactly that... "UNLOCKED". You will be able to swap SIM's as and when you choose. Bell to Rogers, vice versa, or to a foreign carrier when travelling. (My flatmate has an unlocked one, and has used foreign SIM's when travelled to France, Netherlands and Germany). Although, knowing how monopolistic the whole phone industry is in Canada (I grew up here, and still have family here, so I think it's safe to say that I know just how corrupt each telecom here is), who knows what sort of backroom dealings they might have.
Pre-orders started in UK 9 days prior to the offical launch date. I would safely say that if Pre-orders aren't announced by this 27th, it's unlikely there will be any pre-orders taken (especially with backlogs.).
To give a sense of backlogs.... I live in London... They launched the iP4 on the 24th. As of the 25th after they sold out of the second batch of iP4's, they started taking people's names down and added them to a Priority List whereby they'd give them a ring (in order) when the next shipment arrived and had a phone available to them. As of yesterday, there were still people waiting who had placed their name on the list (with 1800 after them). So.... it might be a lengthy wait.
Hope that sheds a bit of light on several iPhone 4 factors.