another way of looking at it...
Due to Thunderbolt, you also have the option to get say, #3, and then add an external SSD in a Thunderbolt case/adapter for use as your boot drive. Some favor this, as then drive replacement/maintenance/upgrade is a lot easier than opening that nice new iMac. Adapter plus SSD drive plus TB cable vs. cost of Fusion drive.
After looking at the Apple options for drives, I ordered a 27" iMac i7, 1 Tb HDD, with the 2Gb graphics card. I'm upgrading the Ram to 32 Gb myself (27" IS RAM upgradable), and I have several TB adapters & 256 Gb SSDs (that I've tested with my MBP Thunderbolt.) which I'll be using to boot OSX and Windows7. SSDs in this configuration are indecently fast, arguably in the same speed category as the $1300 (IIRC) SSD Apple offers. It's been said that via Thunderbolt, you can set up your own external Fusion Drive, although I haven't done it and probably won't.
If you like the speed and simplicity, then the Fusion drive should work for you fine. Or the big SSD!
I'm a designer running Creative Suite Master Collection, Lightwave 3D, Ableton Live, Boot Camped Win 7 64 bit, and I don't even remember what all else. My stance is that since these iMacs are not readily upgradable, one should get all the bang one can for the dollar at time of purchase. I'm totally spoiled (30" Dell Monitor will be second monitor), but I can't imagine not hogging all the screen and ram and processor I can get. If you're a content creator, you'll almost always be glad you did. I've never looked at a monitor and said: "You know, I should have gotten a smaller one" or started up a computer or program and said "Gee, that's just running too fast!"
LOL. Just one dweeb's opinion, but there it is!