The Surface is allegedly more convenient because it's smaller than a laptop, but in reality it's not convenient at all because you have to find a table in order to be productive with it.
If I were going to purchase a Windows 8 tablet as a laptop replacement, I would definitely go with the Lenovo Helix. Unfortunately, it's overpriced and has crappy battery life, like all Windows 8 tablets.
IMO, you'd still be far better off getting the new Air.
EDIT: Another option for a Windows machine would be the recently released Sony Vaio Duo 13. It's got a Haswell processor, a really nice 1080p IPS panel and reviews state that the battery lasts for 10 hours. It's more expensive than the Surface Pro, but it's also a much better machine.
I may just end up waiting on all this to see if Microsoft updates the Surface line with Haswells. Perhaps they'll also address the kick-stand issue. Though with their recent financials maybe the Surface line isn't going to get refreshed?
EDIT: Should also mention I'm right there with you on MBA being the best value. The Surface's main appeal to me is its tablet form factor - I like tablets and have lots of fun using iPads, but an iPad just can't replace a laptop for me and the last thing I need in my life is another device! 2-in-1 would be great.
This is the Helix. It was very close to being a perfect device, but it's held back by a 4-hour battery life. I'm hoping that Lenovo releases a Haswell version, but it might be a while because this one just came out.
http://www.mobiletechreview.com/notebooks/Lenovo-ThinkPad-He...
If the current version suits your needs, google "Lenovo Barnes and Noble Gold", you should be able to get a decent discount.
Here's the brand new Sony Vaio Duo 13. It's a slider, but if that doesn't bother you it's probably the best option for a 2-in-1. The only downside is that the keyboard is only average.
http://www.mobiletechreview.com/notebooks/Sony-Vaio-Duo-13.h...
http://www.dangrossman.info/2013/07/14/summer-workspace/
On its own, the kickstand and not-quite-rigid keyboards make it a pretty subpar laptop for actually coding on a lap.
I have it mostly so I can throw it in my car whenever I leave and know that if a server goes down, or some other issue comes up, I can handle it wherever I am -- it's a full computer but more portable than a laptop. I don't feel the need to carry a backpack or big bag to haul it around in, and I get ~5.5 hours of battery writing code so I don't carry the cord either.
Do you find yourself using the SP as a tablet much for non-work stuff, like browsing the web on the couch or whatnot?
I think for now I'm going to wait and see - The Verge seems to think SP's latest price cuts mean new models this fall. If Microsoft addresses the pain points of SP, I'll take another look. Otherwise it's MBA for me!
- if you want to use it over tables or plain surface is ok, but if you want to use it also on your legs, in train, or whenever you have not a table, it is really problematic. The fixed angle of the support make almost impossible to use it in most of the situation in which a normal laptop is ok
- the screen is around 11'. I don't know if your macbook is of the same size but i would never program in anything < of 13'. That is however a personal thought
- surface pro has a low battery compared to the macbook (almost 3.5 hours) and it has some heat problems