Crossfades and layers
I have just begun looking through the manual at Ardour's capabilities and it looks like it could develop into quite a powerful tool. I plan to play with the OSX version over the next while.
Coming from a SADiE Classic (PC) workstation, I have become somewhat spoiled by a number of features, such as exceptionally fast and full-featured editing (no need for a third-party wave editor; SADiE has its own Trim Editor which can do the most exacting edits, totally non-destructively) plus the ability to burn CDs right from the edit window- just group your edits to form a single entity for each eventual CD track (these can be un-grouped later if further editing is required), and one click produces the PQ flags, which can then be adjusted if required, so there is no need for a third-party CD creation programme either.
One thing I just noticed in the Ardour manual is the business of how clips (regions, soundbites, whatever terminology one uses) overlap and how one will be acoustically "opaque" depending which one is on top. Aaarrrgghhhhh! The AudioDesk (simplified Digital Performer) programme that came with my MOTU interface does this and it drives me nuts! In SADiE, the "clips" (as they call them) are acoustically transparent and it is quite possible to overlap one over the other (on the same track) so that both will play at the join/fade point. I cannot tell you how often this has proven invaluable in smoothing over a tricky edit by nudging one clip by a few ms into the other. (I do mostly classical music where edits are often necessary during continuous music.) The work-around of course is to put one clip on a separate track (or pair of tracks in stereo) but this should not be necessary, IMHO.
I am hoping that eventually there will be a "native" Mac-based recorder/editor with the speed and feature set of SADiE (which is hardware-based), but so far I have not found one. I will soon be evaluating another seriously-professional programme (PC only) called Pyramix Native (from www.merging.com) which looks to have the same sort of features. (BTW Pyramix provides .pdf manuals fo their v4.2 & v5.0 software on their website.)
Neither SADiE nor Pyramix is particularly well-known outside the pro-audio/mastering fields but both are very highly regarded and worth looking at when developing a new, potentially flagship programme such as Ardour. Of course, they are not inexpensive: the 8-track version of Pyramix Native runs about $1200 US and the big hardware-based ones are really pricey, as is SADiE.
However, it is always interesting to see what is coming down the pipe for the Mac as there are a lot of talented developers out there.