There are around 20 open source Java caches. We throw around the term "defacto standard" as a shorthand way of saying ..
Everybody likes to think of themselves as "the standard". What press release doesn't start by claiming that company X is "the" leader in their particular space? ;-)
When it comes to the commercial caches, they have very small market shares but are rich on features and solve important enterprise problems.
I guess it depends on how you define "market share": by number of downloads (silly), number of servers it's running on (reasonable), number of actual clustered deployments, number of paying customers (not a bad measure), actual revenue (reasonable). I personally think that any other solution out there would gladly trade places with Coherence for most of those measurements ;-)
Ehcache has been growing up so it's commercial version can be used as an alternative to the likes of Coherence.
I don't mind that other products compare where they are to Coherence. I love the competition -- and it's often very good (i.e. very tough, very smart, very talented) competition. This is a great industry to be in if you like being challenged every single day to push ahead and innovate and serve your customers well! ... because if you don't, there's always someone working hard to out-innovate and out-deliver you.
From a features comparison for a Java developer, we have almost all of Coherence's features plus a few unique ones of our own like BigMemory and the rich caching APIs in extra modules.
Don't sit on your laurels .. we certainly aren't! Coherence continues to get faster, more scalable, more reliable, more feature rich, better documented, more complete and easier to use with each release.
Cameron Purdy | Oracle Coherence