1. Congratulations for getting it launched. I think the idea is nice but there are many similar sites. e.g. deviantart.com. I hope you have some usp and a plan to compete if this is going to be a startup.

2. Design is nice lookwise, but need some changes from usability perspective. e.g., better icons can be used for categories, filter button is too small. etc.

3. In preview portfolio page, I would prefer to see the actual design first and then description. It would be better if it appears side by side for a quick look.

4. In Start Reviewing list, a small thumbnail of design can make things more interesting. (See threadless.com critique section for details. You can learn a lot from threadless model)

5. Why separate review screen? Can't it be done in intial project page? Try reducing number of clicks wherever possible.

6. Instead of drop down try star ratings. It's quick, easy and well accepted. Put rating widget and buttons in one row. Make comment textarea small. Don't make user scroll if not necessary.

7. My flash plugin is either outdated or corrupt. I'm unable to upload images on site. Basic HTML version of file upload?

Overall, nice try. Keep improving and be prepared for competitions. All the best.