My Fisrt Knit!

I am learning to knit! I had this in mind for some time now, and finally I had a good excuse to get something to do when I am not home and I have loooots of time to kill while I chat with other people and reading is not possible.
I have a teacher too. A girl from my place offered knitting and crotched classes every monday at a different bar. 

So we bought this very thick wool and circular knitting needles number 12. First I made the short buttoned scarf, practicing two kind of different stitches. When I finished, I made the circular hat, dicreasing and cables included. I liked it a lot. Thick wool is fast to knit! I am now starting my third project: a pullover! But this is a long term project.

I feel so clumsy! But everybody tells me, I will improve with time. I have serious doubts regarding needles. My teacher recomends me to use the circular needles for every project, but other experts say that they have to be used only for circular projects, and knitting with the thread in the left hand. I will experin¡ment with both circular and flat needles and try to decide what is best. 
Are you an expert knitter? what do you think reagarding needles?