I have a 2013 MBA i7 1.7Ghz, CPU feel fine for graphic editing, web development, and some X Code. CPU still feel fine, I'm only upgrading because of the Retina Screen and I do a little bit of FCPX. Your usage sound a lot less. I paid $5 for something called CPU LED that has little bars telling me how much the CPU is spinning.
Honestly, there's very few times my CPU spin all 4 bars to 100%, and that's the only time a little big extra CPU helps. The other 99%+ of the time, the CPU doesn't hit 100%. When it does, the differences, if any, is in the milliseconds. Think of it as the i5 spin at 80%, and the i7 spin at 75%, and they'll both do the same work in the same amount of time. You're not saving time, all you paid for is a CPU that run about 5-8% less on the bar. It's when you run the i5 at 100% with a queue and the i7 can run that at say 99%, then and only then do you get that 4-7% time saving.
Unless you're a graphic artist and you've got 500MB master files that are designed to go on 60' billboards or something, you'll never even notice the difference. The new MBP CPU is roughly about 15% faster than my 3 years old MB Air. Only maybe 0.1% of the time using the MBA do I even run my CPU over 75%. Even at a 8% compounded gains on CPU speed, it would take 5 years for the CPU to be roughly 47% faster. And we've been averaging around that, sometimes a little bit less even the last 3 or 4 years. The RAM's a good choice, and the SSD size may determine when your next upgrade need to be far more than CPU speed.
