What is the difference between havingor having not SSD to an ultrabook?

Q. I found a lot of u ultrabooksare with SATA drive. So, ssd, is it big deal?

A. SSD are nearly 200% faster than a SATA HDD. An HDD has more storage capacity and a decent speed. (1-2 TB for 300$) A 128GB SSD is approximately 109$ To answer your question:

Yes, it is a big deal :)

Will a sata iii ssd work if i want to upgrade the ssd on my asus ultrabook ux31a?

Q. 128gb isnt enough for me. I want to double it but i dont want to cheap out on a sata ii ssd.

A. It WILL work, my friend, but the data throughput will be limited to SATA 2 speeds.

How well does an ultrabook perform in terms of heavy programming?

Q. Heavy programming in the sense multiple Visual Studio windows open at the same time as well as chrome and eclipse.

A. I don't know what the specs are of the ultrabook

Eclipse and visual studio are both memory hogs.
Try to get a system with as close as possible to 8 gigs of ram with either an i7 or i5