I do eCommerce for a clothing company and for my personal projects; the main things that mattered to me for hosting were:
1. Ability to get at least a little support/direction from my hosting company.
So from personal experience I have be hosted for more than 6 months with dedicated servers on godaddy and 1&1 hosting. I was not really impressed, both had awful customer support/technical assistance. 1&1 was slightly better in that their servers were noticeably more robust than godaddy.
Frequently the main response received from godaddy if you are experiencing any issue is upgrade your server or hosting; but even using their best services you are likely to notice regular slowness on VPS as well as dedicated servers.
2. Compatibility with the CMS or eCommerce solutions I plan on using.
Again another personal example, when I decided to go with Magento as an ecommerce solution at my company, I looked up who had made an effort to be extra compatible with it. I found that hostgator specifically is recommended for magento and advertises on the basis that their servers are 100% compatible from the get go.
On top of this after going with hostgator I have found they by far have the best support, often going above and beyond what they are responsible for as a host and simply solving your problem.
bottom line, do research for hosting companies that work well with specific ecommerce platforms, because they are a big struggle unless you are very familiar with them, they are more difficult to pick up than CMS.
Hope that helps
Lucas