Enterprise Service Bus (ESB). Nice name. Every time I see something with "enterprise" in the title, I get the "ooh"s. Or is it the "aah"s? I simply can't walk past a book titled "Enterprise blah blah" without stopping to thumb thru it. It's only $59.99 and it's shiny. Should I impulse buy it now or add it to the Amazon cart for later?
ESBs. I've messed with a few of them, probably used Apache's ServiceMix the most. Using servicemix, I had a Groovy SOAP server working with a JMS app in about 10 minutes. Maybe it was 15. I tend to exaggerate. Whatever time, it was short and servicemix was easy. Speaking of MQ, have you read Linda's Open Message Queue Blog? It looks pretty good but she hasn't updated since October 2007.
Some guys at work are using BEA's Aqua Logic. I've not had the chance to use it but they seem to like it, especially the message transformations. I've got a demo disc sitting on my desk and anyone can download a demo. I should test drive this soon. Last summer I used both JBoss and WebLogic JEE servers and I found that WebLogic was much more stable. I think the price is a little steep for mortals but the product was better.
There's also Mule which I've never tried. I've stumbled across an interesting article "Exploring ESB Patterns with Mule". Yet another thing to work thru and try out when I have a spare hour or ten.