It is very prone to crashes and hangs when anything with the transport
goes wrong, and it's not exactly trivial to restart transport.  Its

I use Mixbus (2, 3, 4, and now 32C),  and Ardour 3.  I build the current source from time to time to keep abreast with Ardour but don't use it for production work.  I don't get crashes, not from Ardour anyway.  Sometimes when running lots of my hare brained Pure Data and Csound and hack homemade JACK clients I wrote in C all wired together I can crash the machine.  Ardour always comes back up in the state I left it in. 

 
autosave does not just leave a recoverable state but actually saves the
whole thing periodically as the current project, so if you don't know
whether you actually want to commit (or are pretty sure you don't) you
have to turn it off, or quitting without saving will leave you in some
unpredictable state.
 
Again, I find Ardour recovers from crashes almost perfectly.  Maybe with the latest versions they've broken it.  

 
I recently had a demonstration where the mics were wired wrong and so
the two "stereo" channels I recorded on were mixed up.  You think I
managed to split the tracks into mono in order to salvage two usable
tracks?  No beef.  I'd have had to do a stem export and reimport.  Or
something.  Didn't really fit in the demo time frame.

You can flip R for L a few different ways.  You can also split the file in to two mono files.  You absolutely do not need to stem export and reimport.  I'd be happy to show you how some time.  It's easy.  Ask on IRC.

 

Handling marks (setting, moving them) is always hit and miss.
Manipulating automation with the mouse is hit and miss.  And so on.

I don't  know what this means.  I don't do a lot of automation but I absolutely use marks and moving them and bouncing around between them.  Works fine here.

 

It's when you start editing that things get awful.
 
If you say so.  I edit like a motherfucker with Ardour.  Only system I'm faster on is a legit Protools rig on an adequately powerful Mac.

It's all kind of a moot point though, because it's the only actual option.