This is not a criticism but the thing that I don't understand is why people such as yourselves waste your time venting your anger here. You need to use the Apple Feedback (someone mentioned it earlier in this thread) to let Apple know your dissatisfaction, especially if it means you are not considering a new iMac anymore. Don't rely on Apple reading this forum. They can't because there is too much going on on these forums, so they don't.
That said, I didn't myself upgrade from my 1998 PowerMac to an iMac until late 2007 so I got a good nine years out of it. So you don't really need to upgrade if your iMac is nearly three years old if your don't want to. I'm using my late 2007 iMac now. It's fine for everything as you can see. I'm here (except that I regret going from Snow Leopard to Mountain Lion in one go for a number of reasons that I anticipate are going to take me months to sort out).
As for the SD card issue, I don't have an SD card reader on my iMac. I use an external USB Hub (powered) that I plug a universal cards reader (cheap as chips). I find even plugging an XD or SD card into one of these readers fiddly enough when they are not plugged in to my USB hub. So I can imagine how difficult it must be to shove these cards in when the slot is out of sight behind the iMac. What I can't imagine is how difficult it will be for poor killhippie!
External DVD Writer/Recorders are fine. I have one. Trouble is, they are mostly USB 2. Mine won't work with my powered USB Hub. It only works plugged into my last remaining free USB at the rear of my iMac. So the new iMac will need to have plenty of spare USB slots at the back to cater for my existing kit. I suspect that it hasn't. If one wants to copy directly, disk to disk, one will need a dual bay drive I reckon. I don't know if any such beast exists.
One thing I do think is that the new iMac is no longer the true All-in-One device that it was. My impression of the new iMac is that it is like paying for the biggest fish in the shop then getting it home only to find the tastiest bits have been removed to make way for a huge metal hook.
Speaking of huge hooks reminds me that there is much talk about the new iMac's start up speed due to SDD. I wonder, how much have you guys heard about the "finite write capability" of these devices? Not a lot I expect.
As I understand it from other websites, SSD's are not infinitely rewritable like HDDs. They may only be written to so many (finite) times. Hence software like Fusion is necessary to limit the use of SSDs to apps that may be opened as many times as one would care to wish for but virtually never written too. Items such as, such as Apps. Bear this in mind when you read what Fusion actually does.
When purchasing new computer kit (not just iMacs to be honest) if the manufacturer claims ultra fast start up speeds due to SSD, this seems to be something that one needs to be aware of.