Linux Journal has a nice article about the current state of Ardour that is well worth a read. In it, Dave Phillips describes a number of projects that are tied in to Ardour to provide enhanced functionality and the ability to tailor Ardour to specific needs. The focus of the article is mainly on the development branch (Ardour 3) that is not yet available through regular channels yet, but it very clearly shows that professional Linux music production is moving forward fast.
There is one thing I should mention though: in the article Dave says that the current official release of Ardour (2.8.11) is not available in most distributions. While this is generally true, there are cutting edge releases that do have the latest Ardour available. I use Arch Linux and thus have the latest stable version installed. Although being on the cutting edge has its disadvantages (occasionally things break), developments in Linux music production are happening fast enough to warrant it. More information about my motivation is available here.