Documentation is outstanding. Pricing is concurrent connection based. Despite rumors to the contrary, I also use Microsoft products. Internet Information Server is available with NT Server. It is easy to set up and maintain.
Remote administration can be a hassle.
Well supported and documented. If you are on NT, or considering NT- this is the way to go. Last time I checked, free with NT Server via Service Packs. In order to really conduct e-commerce you will also need to obtain a certificate from a Certificate Authority . This allows you to prove your site is operated by who you say it is.