In the truest sense of the word, only those who have already bought are in a position to help ... and that is very few as of now. But ...
If you want to do your head in ... there is a thread (link below) which will give you many views on the facts known. It's worth scanning through, however casually.
Wish you well
I can speak to this one, having just taken delivery of my new 27" iMac w/Fusion Drive on January 2nd.
My initial impressions are that the Fusion Drive results in much faster boot times...normally less than 15 seconds or so. The display is a big improvement over my early 2008 24" iMac (although I wish they still offered a 24" model...I really don't need 27"). The speed improvement is nice as well...I rarely see the beachball anymore.
I remain puzzled, though, on why Apple felt that making the iMac thinner was a big design improvement. From the front, it looks identical to the older iMacs. And, making it thinner required ditching the optical drive and moving the SD card reader to the back of the device. I can live without the optical drive (I had to buy an external Superdrive, though!), but moving the card reader to a very inconvenient location was a step backwards in my opinion.
Overall, I'm VERY pleased with the new iMac!
Thanks for the reply Mike. Glad to hear you like the new machine - it does sound, from everything I've read, as though the Fusion Drive really speeds things up
How much RAM did you get? I would be getting a 21.5 model and I've no idea whether to upgrade to the 16 GB or leave it at 8GB. I don't do much video editing but I do a lot of sound editing and music work
I agree that the obsession with thinness is puzzling. I think it smacks a little bit of desperation - in the sense that they realised the iMac looked pretty amazing as it was and all they could do to create a new design was have thin edges. As you say it makes no difference to how it looks from the front. If the entire machine was 5mm thick now that would be amazing, but given that there's a massive bulbous shape at the back it does make the fact that the edges are thin seem a bit pointless
I got 16GB of RAM with mine (although, in hindsight, I should have configured it with only 8GB and upgraded the RAM myself).
For the 21" model, though, I would max it out at 16GB, since the RAM's not user upgradeable on that model. Especially if you're going to be working with music applications like Garageband and the like. (And...when was the last time Apple introduced a new OS that used less RAM than the previous version?).
Just my $0.02 worth.
These may help you:
Review and comparisons between the 21.5” and 27” new iMacs:
MacWorld review of 27” iMacs with different hard drives (surprising results):