I've been using your site for a while now and I have to say that I love it. I have long been a fan of social bookmarking, but must say that I love the idea of sharing sites and ideas visually, and the layout is very aesthetically appealing.
However, there are a few things that I believe need some additional attention and/or removal.
1. The phrase, "Pin now, read later" has got to be the dumbest, most annoying phrase ever. No, I want to read everything this page has to offer now! Come on, people. It has to go.
2. If I see one more "How to use your baby's footprint/handprint/thumbprint/whatever to make some cute animal/character/necklace/whatever", I may just scream. It was cute the first 20 times; now it's just annoying. If anyone actually attempted all of these ideas with his/her baby, the baby would constantly be covered in paint. I believe my mom did this ONCE with my brother and me; not once a holiday, not once a season, ONCE.
3. It's cool if people want to reuse the pin description from another pinner, but please at least urge them to read it over first and make sure there isn't personal information in there that wouldn't apply. Though, it does make me chuckle when a guy I know to be straight or an unmarried woman shares one of my pins I have labeled, "My husband would love this".
4. Pinning from blogs is great; I love getting to experience new blogs, and have discovered a few worth reading regularly through Pinterest. However, pins for a specific blogpost should link directly to that post, not to the main page for the blog. To do this, click on the title of the blogpost you like; you will be taken to the permanent link for that page. Then pin away. The main blog page is a feed; it shows the newest post (whatever it is). The post you like may be the newest post when you visited that blog (and therefore at the top), but by the time the pin gets to me, it's 50 posts down the list, and I have to do some digging. Sometimes, I can find it with a google search; sometimes, I just give up.
5. Not a complaint, but a suggestion - it would be cool to browse pins on two topics, rather just "Geek" or "DIY & Crafts". Because I'd die from excessive happiness if I could browse a board full of Tardis scarf patterns. No lie. Yeah, I know I could just google that, but the cool thing about pinterest is discovering things you didn't even know you should/could be looking for.
As you can see, this list is short. So it should be no problem to meet all my demands... er, requests. I'd consider it a Christmas AND birthday present. :)