I signed on to every waiting list I could find for MTN, Vodacom and iStore. MTN I pre-registered in the first 2 hours when the opened it up, never heard from them again. I also pre-registered and wait-listed for the iPhone 4S round long ago, also ended up waiting 2 or 3 months before hearing anything. My conclusion is that waiting lists and pre-registrations are useless and ignored, unless you "know a guy" or bribe a guy. Vodacom came out on top though, they did eventually call me and I placed an order with them. They warned me about stock levels and even suggested that I pick Silver to get one sooner. So next time round I'm just going to order the thing online as soon as possible rather than chasing around in angst staring into the blank uninterested faces of store employees (again, some of them were good, iStore mostly).
I phoned MTN Direct for an upgrade and received my phone within 48 hours. They have all the colours and sizes.