Load times - Even though many people have high speed internet access, many people don't (about half of your potential customers). If your site takes a month to load then they aren't going to wait.
A great place to check your load times can be found at the following link -
So how can you speed up your site -
1) Keep flash etc. to a minimum.
2) Optimize your images.
3) Use thumbnails if you have a lot of images - make sure that you have two images saved - a large one for when folks click on the link and a smaller one for the thumbnail - many times I've seen sites that have both saved as the same image, that basically defeats the purpose.
Have a good one.