I have owned all three versions. The other reply was partially correct.
The Rev C differs in these ways.
2.13 GHz SL9600 Penryn Intel Core 2 Duo
Nvidia GPU running 6x original (rev B was 4x original)
Battery has more capacity AND allows far more cycles (I am getting 45 more minutes on C than my rev B 1.86/SSD)
Network adapter to USB included.
The display in MBA is same as in rev B. Most of the lines are visible from short distances but not normal viewing. The GAMMA 2.2 setting helps in my opinion. To me about 20% of the displays have visible lines from normal viewing distance. Most cannot see as it appears grainy but not a problem very often.
I highly recommend you buy either rev B/C with SSD. Can be purchased in refurbished section at Apple.com for $1349 and $1549.
I am very pleased with the rev C. I will not be surprised to see a new high-end between now and November.