In the early days of workstations and servers, the size and weight (aka thump factor) of a hardware vendor's application catalog was a frequently used and effective marketing tool. More applications = More Solutions = More Sales. These days, vendors (including Sun) continue to tout the size of their application catalogs. Matt Asay from Alfresco wrote an article in CNET recently commenting on the virtual-thump-factor wars between Novell and Red Hat.
Solaris has had a long history of working hard to make sure that its application catalog is both broad and deep. The listing available here shows a total application footprint of 11,225 applications available for the Solaris platform and of those 7850 are for the x86/x64 platform. This is significantly more "thump" than the current Red Hat catalog. Red Hat argues here that there is an 80/20 rule in which 80% of customers use the same 20% of applications. This is true only to a point - our customers know that there exists a long tail of applications that may not be big names, but are nonetheless critical to operations. Although most of the applications are common to most customers, each customer usually has a couple of special applications that have crept their way into use and are indispensible. In the end, *thump* still wins.
Sun has also constructed a software catalog community which is gaining publishers by the day.
