The most important thing is up-time – Approximately everything is bearable as long as a web site is up and functioning instead of downtime problem. A little downtime like for couple of hours in a month is acceptable due to some technical issues but more than this is not. Every web host make excuses like downtime is unexpected and unexplainable. If site is down for a specific time period it may result in affecting visitors. Webrings most of the times check out the broken rings through their specific code, point out the down sites and finally delete them. Search engines also remove the down sites after a specific time period. And obviously visitors will remove the site from their favorites if the site is down for longer time.
Secondly most essential thing is performance – Well, server you use should have enough power to maintain all the web sites run smoothly. This will increase your profit as the sites are running in a pretty good way. Overloading server can be fatal and result in failure. Servers actually require frequent maintenance to work properly and avoid any unexpected crash. Let your customers know if there is any upcoming change in your site that will increase the incredibility of your site. Most of the times server slows down when any up gradation occurs, so don't do any experiment on your production server. Visitors need your site in working condition ever second.
Webmasters don't want to pay for poor services from any web hosting company. So web hosting companies must care about them and should provide services keeping these points in mind. No one want lose customer in this era of technology at any cost.