Macbook Air 13" as a complimentary laptop?

[akshtray]

My main laptop at home is a Alienware M14x (2nd gen i7 with 8 GB of RAM). I do have a Desktop as well (core i7 + 8 GB RAM) and a older Core 2 Duo based server that I use for media streaming/storage purposes. I am looking for something lighter which I can use while sitting on the couch for tasks like:

- Web browsing (the most extreme case most likely being youtube videos)
- Scripting (main reason for looking at a laptop which is portable. Python, PHP, etc) so a GUI based editor like PyCharm, Eclipse, etc.
- Email (web and built in Apple client)
- Maybe 'Office' software like Works, etc. Viewing PDF's
- Once in a while watching some .mkv, .avi video files (720p/1080p)

I will be getting the Air using my Best Buy credit card + rewards. The main question I have is if the 4 GB of RAM will be enough for my requirements? I would be all up for spending $100 more for 8 GB of RAM but Best Buy does not appear to stock those.

Thanks guys.