Well, I found in incredibly hard to find 'Add to Cart' button your site. On your product pages, you should move it to top and make it really prominent on the page (maybe a different color, how about red?). Plus, your product pages lack brief one line description. Ideally, I would like to see what a product is just below the product name. You have paragraphs and videos but not brief description. ou should emphasize the discount given. For now, I have to mentally calculate how much I am saving. Why can't you tell that directly on a page? You are also underplaying 'Free Shipping' aspect. It is a big, big advantage and should be written right next to the price.
After I add product to a basket, you should swap the order of buttons in the popup. The checkout button should be displayed above the continue shopping button.
Lastly, your checkout page: if possible, add tax in the price itself. Visitors don't prefer surprises on the checkout page. No where it was obvious to me that you were going to do that. Please avoid that or mention in price something like 10% tax extra (or better still, add in the price and say all inclusive).
Then you ask users to register with the site but you do have a express checkout as well. I would test eliminating that step. You should be able to detect a repeat visitor from cookie or something, so ideally should show that step only to those visitors. Lastly, try to take all information in a single step (that is shown to increase conversions).
Hope that helps!