They aren't big - but they are bigger than when it was just Urs and a couple of guys turning out plugins.

They becoming popular on the back of Diva, and Hans Zimmer using Zebra (he's very fulsome in his praise whenever mentioning u-he in interviews).

I guess big as in widely impactful.

Making a new plugin standard that is gaining wide adoption is big in my head.

They make a lot of great virtual instruments nowadays. Diva being a big one.

I like my old ACE, but people with better ears than me say that the sound engine is not as good as some other U-He synths but it was more in my price range and I wanted something good enough but without DRM. U-He was (is?) one of the few makers of audio software that did not rely on some online registration or USB dongles (plus Linux support as a bonus).