I chose the upper end but I generally agree with those who have commented ahead of me. in my case I also play a fair amount of video games, so I felt that the extra bump in processor would help that little bit extra with framerates. I wasn't mistaken - I'm finding that I do a bit better than the slower macs, and at a lower temperature, generally. But for everyday applications? No discernible difference.
Also, the CPU is one area that can't be upgraded, so that was also a factor, as I hope to keep this computer for a few years. Hard drive and ram, well as others said, it's easy to do yourself and it doesn't make sense to pay Apple to do it. That and I do know that I'll be watching as the SSD prices continue to fall and SSD capacities continue to rise.