Yes the feeling of completing the first instance is a blast. I would strongly suggest you run the instance again, since you will find you have improved quite a bit in skill.

I cleared utgard keep for the first time last weekend. It was a blast. I also spend hours on the first run wiping all over the place, but I had a great time.

I headed back and did the second run much much faster. In total I have done the instance only 4 times, but I could see a bit of improvement everytime.