I also used to have doubt about it because I heard it was categorized as a "log analysis", which is very unsexy from a developer's point of view. Can we be tricked by names! After using it for a while just yesterday, I found it not bad at all.

In a nutshell, Splunk is valuable because it turns your unstructured untyped data into something much easier to analyze and Business Intelligence (BI) ready. IMHO, the strength of Splunk is two folds. First, it provides a central place to view and mine your logs across hundreds or thousands of machines. This is very useful in many organizations with large scale distributed computing because you don't need to ssh into your database server in one terminal and compare the results in another terminal connecting to your web server, if you could ever figure out which of the 100 database servers you should look at. Second, instead of just greping, it treats each log entry as a list of key-value pairs and provides a simple yet powerful query language for it. On top of that, it gives you a library of visualization components. I was able to build a fully-customized Google Analytics style dashboard for my application in 20 minutes. And I would say that is empowerment, and empowerment is the most valuable value.

And if you are very into technologies, they are a Python house, which is always a plus :)