The definition of "pro" is relative. This thread is nonsense.
Ha-ha, true

What does pro in your user name means by the way?
I consider myself a pro because I use computer for my professional full time activities.
I do:
1. Some iOS (iPhone) development (natively on mac). Relatively easy task for the hardware.
2. Java Web development (natively on mac) - very memory and CPU intensive. Using memory swap is not an option.
3. Windows OS development (Virtual Box VM + MS Windows OS + MS Visual Studio) - relatively easy task as long as enough RAM is provided. Using memory swap is not an option.
I deal with video encoding, but that's home movies on occasion once or twice a year.
#1 is the reason why I need mac. Otherwise I could save lots of money and buy PC hardware with much more power. I'm also a little tired of Windows and want something different. Linux is not refined enough for me. I like Macbook design.
* Memory:
For my current tasks 4GB is just enough at the lower edge. I can do either #2 or #3, but not at the same time, as either of these tasks uses all memory. I did not buy more memory from Apple as it is cheaper to upgrade elsewhere. I will upgrade later, when 4GB will not be enough and I will know how much extra I need. I'm pretty sure at some point 8GB will not be enough. If I decide to work on #2 and #3 at the same time 8GB will be at the limit even today. And #2 and #3 grow in memory the more time you use them. (Air is a no go).
* CPU:
i5 has reasonable power. #2 builds around 2 times faster than my Macbook white Core 2 Duo 4GB does (which I still use as secondary dev. box). #3 builds slightly faster than HP Core 2 Duo laptop with Windows OS that I also have but would like to decommission and use single hardware. i7 would do better, but not enough to justify extra spending. And any CPU will get outdated soon, so no reason to pay big bucks for the top one. Also, Apple doesn't give us the best of i5 i7 anyways. (Air or Pro - are even here)
* Hard Disk:
#1-#3 does intensive and extensive disk input/output all the time, and I'm concerned regarding SSD longevity with its limited write cycles. Also, #3 takes a lot of disk space. (Pro wins over Air here). I do appreciate SSD's speed, but more importantly - mobility as there's no risk of loosing the information while using the laptop in the motion. I can install SSD if this becomes important (Pro wins again).
* Battery:
I do use the battery a lot, and ability to replace it makes lots of sense. (Air loses).
* Screen resolution:
Doesn't matter much as long as it's reasonable. Screen size plays bigger role. (Pro and Air are equivalent for me on this one)
For anything other than #1-#3, like web browsing, photo editing, document\spreadsheets and even video editing my MacBook white with Core 2 Duo does perfect job and I feel over-powered.