If you receive an offer from your first interview, congrats you have done it. If you don't then its a definitely a good sign. I learned a lot by giving many interviews. Yes, I was frustrated by the fact that I wasn't able to crack the coding interview. But, I was becoming a better judge of my skills and I was able to concentrate on the weak links. I became confident of giving interviews and when I started working at Ariba the confidence was very well reflected in the quality of code I started to write at work.