Accessed has The Forrester Wave: Enterprise Service Bus, Q2 2006, By Ken Vollmer and Mike Gilpin, at Zdnet Whitepapers (via Cape Clear).

Below are some excerpts from the same:

Forrester's definition of an ESB is:

Infrastructure software that makes reusable business services widely available to users, applications, business processes, and other services.

THE ESB IS THE LEADING ENTRY POINT FOR IMPLEMENTING SOA
Forrester expects to see 67% of firms with 40,000 or more employees implementing SOA this year, and 44% of small and medium-size businesses (SMBs) already report that implementing SOA is a high or critical priority. Nearly 70% of users say they will increase their use of SOA, while only 1% of users will decrease their use. The data also shows that most firms - 83% - are using SOA for internal integration. This data reflects a perfect storm of market conditions to drive the growth of ESBs, which are the most straightforward way to get started with service-oriented integration today. ESBs are also typically less costly than other ways of doing integration, such as integration-centric business process management suites.

Forrester evaluated leading enterprise service bus (ESB) vendors across more than 100 criteria and found that Cape Clear Software and BEA Systems were the top two performers overall. Other vendors in the leader category (from the highest score down) are Software AG, Progress (Sonic), IBM, and IONA Technologies.

Source: 1

Prashanth Rai