My most recent tech purchase over $500 was a computer. Specifically an HP Envy x2. One of the reasons: amazing battery life. Twelve hours or so. The catch: the darned thing pokes along due to an Atom Z2760 CPU. But it’s also $580 so that’s forgivable.

My workhorse notebook is an early 2009 MacBook…with a few upgrades. It’s got the 2GHz Core Duo CPU and nVidia 9400M graphics…backed up with 8GB of RAM and a 256GB Crucial m4 SSD. It’s not the speediest machine out there, and I can’t seem to find a decent replacement battery so I can only get three hours or so away from an outlet, but with the RAM and disk upgrades it’s actually reasonably fun to use.

Why did I just bring up two pieces of old/low-end equipment that have nothing to do with the current MacBook Airs announced a couple hours ago, other than screen size? Because replacing both with a 13-inch Air isn’t out of the question for me…later this year, once the newest OS X edition comes out. That said, there are a few specs that got glossed over during the presentation today, amid all the talk about power efficiency (nine hours on a charge for an 11-inch machine, or twelve hours on a 13-inch, is just excellent). Stuff like CPU speed and upgrade costs.

First off, the two Air sizes are identical in every other respect than screen size/resolution and battery size/life. You can upgrade the 11.6-inch model (with a thoroughly standard 1366×768 LED-backlit screen…no Retina on either size) just as much as you can the 13.3″ one. The display on the 13.3″ model hits 1440×900 for resolution, just like its predecessor. Size and weight specs are the same as the previous generation, too. Upgrades on one component are independent of upgrades on any other…no need to buy the 256GB model to get a faster CPU.

Second, CPUs on the new models are on the slower side, though I’m sure they’ll still run faster than my four-year-old MacBook’s…at least I hope so. Both options are dual-core; the base i5 is an Intel 4250U that sits at 1.3GHz but will max out at 2.6GHz if thermal and power constraints permit. $150 buys you an i7 (again, only two cores) clocked at 1.7GHz (the 4650U), revving up to 3.3GHz when TDP allows. If I were to buy the Air, I’d spring for the i7; the base model’s CPU just isn’t anything to write home about (except for power consumption), while the higher-end model should fare well enough.

Third, the system comes with 4GB of RAM. 8GB is $100 extra. Add that to the list of upgrades that I’d want to make if I bought an Air; I certainly don’t want less memory on my mobile workhorse than I have now.

Fourth, you can get 512GB of storage with the Airs. it’s just $300 more than 256GB, which is in turn $200 more than 128GB. Since I have a desktop for my primary machine, 256GB is enough for a mobile workstation (and yes, I’d use the Air as that), including dual-booting, but 128GB isn’t.

So I’m looking at a $1550 computer if I wanted to go with an Air. Less expensive, lighter and better battery life than a 13″ Retina MacBook Pro (I want something in the 13″ range…or a 14″ model with a 13″ footprint), but the Retina Pro would have significantly more CPU horsepower. Probably even more so soon, as I can’t imagine that a Haswell refresh to the line is too far away.

Also, just to throw this out there, you can get a pretty high-end Windows ultrabook for $1550…