I'm having mine sent to the Apple store since no one is normally here to sign. Also, I wasn't sure when it would arrive with it coming during Christmas week so it seemed like the best option.
mperdue, I opted for the i7, but left the RAM and drive at default. I had bought a LaCie 3 TB Thunderbolt drive last Black Friday from Apple (got one of the Apple gift cards that went against the iMac's total price) so I would have enough room for videos and photos. I had been planning to get a new Mac for the last year, but it never happened. RAM is upgradable, and iFixit as well as OWC sell kits to allow replacing the internal hard drive, but not until the warranty and Apple Care are history.
The other "splurge" I made was in the GPU. I tried to read as many articles as I could to get an idea how the two GPUs compared to each other, but the only arguments I found were some reports of occasional stuttering on the stock graphics, which could easily be explained by a Yosemite issue instead of a GPU issue.
BTW, the one thing that helped push me toward the 5K Retina iMac was the dual Thunderbolt 2 (20 Gbps) ports. The refurbished iMac with the 3.7 GHz i7 I had my eye on is the 2013 model which is equipped with dual Thunderbolt (10 Gbps). I hadn't seen that mentioned in too may reviews, probably because there still aren't that many peripherals that take advantage of it.
Also, I'll be curious if our iMacs are Made (Assembled) in the USA. I thought I heard somewhere that they are. When you get yours, check the labeling.