In terms of some of the organizations I know that are using it: IEEE, NetFlix uses it for many internal apps, Target, one of the largest hedge funds in NY area, LiquidNet. I think there are less publisized stories about it because it is more focused on enterprise, which naturally is less open about what they use. However, the community is great, there are a ton of plugins, and VMWare has done a good job continuing to support it as parts of SpringSource ecosystem.

It's the same way that there are so many Spring / Java apps being written out there (including in startups), but they rarely come up on HN as opposed to some of the newer kids on the block, ala node.js or rails.