I would suggest that for visitors the key factors would be speed of loading:
- not too many graphics, eliminate large unnecessary graphics (esp. those in excess of a few hundred kb);
- accessibility – is it easy to find the key pages in the website;
- pricing – I HATE browsing websites and finding that the pricing is unavailable (what have they got to hide?) esp. when it is for goods or services that are traded over the Internet or are Internet products/services. That seems especially dumb.
There are a few other things I have noted in the years I have surfed, but those are important ones to me. A general tip: if it annoys you, it’s quite likely that it annoys others, so don’t repeat the mistakes on your own website.