I'm excited about this feature, and I thought I would give it a try right away.
 
I first tried it on an electric rhythm guitar part which is pretty distorted. The results were disappointing, i.e the tempo map was all over the place, even though the recording was done with a click. But then, I can see how a distorted waveform could make things difficult for the algorithm; probably better to record a DI track in parallel to a mic'd track if I want to generate a tempo map.
 
I then tried it on a project that started with the singer/songwriter playing acoustic rhythm guitar. In order to be rhythmically "free", the performer didn't use a click, and it rushes and drags a lot. Also in the project are lots of other audio tracks that I've managed to get to sound good with the original track after much work, since it was hard for everybody (especially the drummer) to overdub on to the "free" track.
 
A tempo map was generated, varying about as expected. But now the other tracks are out of time! Apparently changing the tempo map changed the playback timing of all the other tracks.
 
What I was hoping for was to see the other tracks play back exactly as they did before, and to use the new tempo map to fine tune some of the timing of those tracks. But how to do this?
 
I'm sure I'll figure this out, but I'm hoping some of you are ahead of me.

A follow up, in case it's helpful...
 
I copied the acoustic guitar track from the original project into a new project by itself. I then dragged the clip to the Timeline, and generated a Tempo Map. It worked great; the waveform transients are lined up with the vertical markers throughout the song.
 
Next, I copied (Events in Tracks only) a percussion track from the original project into the new project. The timing is now very close, whereas it was wildly off in the original after generating a Tempo Map!
 
EDIT: vertical, not "horizontal"

I confirmed that copying and pasting tracks from the original project (Events only) into the new one with the Tempo Map created for the acoustic guitar track results in a project lined up with the beat lines and playing beautifully. For interest, I generated a click track by stretching out one bar of quarter note cowbell hits (Groove Clip'd), and the click stays right in time with the music, variable as it is.
 
This is great!
 
But I still wonder if there is a way to generate a Tempo Map from one track in a project, and have the existing tracks continue to play as they did before. This would be a lot easier than copying all the tracks to a new project, and would make tweaking of the timing in the project much easier.
 
Perhaps the conclusion is that you have to generate the Tempo Map before immediately after tracking the "free" track, before doing anything else. It's not clear to me why that should be.

Hi Vanceen... this sounds like something I could really use, since I "free form" to lay down an idea, then want to build around it. You mentioned "A tempo map was generated... " from a freely played acoustic guitar. How do you do that?
Thanks!
 

Billy, I believe that you need to use the purchased version of Melodyne that includes the ability to create a tempo map of the audio track(s).  Once that is done, you can drop the tempo map onto the timeline of the Sonar project and the tempo from that track is now your tempo in the Cakewalk project.
 
This is very exciting for its usefulness is something that will save me (us) hours of trying to manually create a tempo map lined up with an audio track.
 
I have already updated to Melodyne 4 in anticipation of this new tool but personally will wait for the official SPLAT version to be released before I try it.
 
Thank you NANCEEN for the play by play on your experimentation. It will save us all tons of time trying to work all these details out.
 
Jim

I think what you can do is either set all the other audio clips to be groove clips (so they bend to the new tempo) or make all audio clips Melodyne FX regions and inside there tell it to use the DAW's tempo (not sure about the original master track, it may need to be made into a loop or a region FX also). 
 
To do that in Melodyne I think you may need Editor 4 or higher (unless all the other audio clips are monophonic?).  I played with this just for a few minutes with a vocal track and some MIDI drums, didn't try with a second audio clip.  It does seem like it opens some interesting possibilities.

I dragged the guitar clip up to the Timeline. That's all it takes to generate the Tempo Map.
 
I'm using Melodyne Studio, but I think it will work with other versions.

OK here's what I'm seeing.  I have a vocal clip.  I drag it up into the timeline and now I have a tempo map.  The visual of the track will have changed because the M:B:T have changed but the audio on playback is still the same.  If I bring in another audio clip, it plays the same, the tempo map doesn't change it at all.   If I change that other track into a groove clip or turn on audio snap though things do change, the sound of the second clip tracks the tempo map.
 
When you said your other tracks had been fixed, did you do the fixes with audio snap maybe?  If that's the case you may need to bounce them down to new clips since it looks like audio snap and groove clips track with the tempo.  Which to be honest seems strange since I'm not checking the "Follow Proj Tempo" on the Audio Snap but it's definitely changing my other audio clip.
 
I think I'm going to make some various length and speed click tracks and then see if I can work out how this process works.  Still not sure how the multi-track tempo features in Melodyne Studio actually work.  Those videos on their site are very hard to actually follow from a here's how to do this thing point of view.

Tempo maps are best created from a bass line or the kick and snare. Vocals can dance around the timing.

elegentdrum
Tempo maps are best created from a bass line or the kick and snare. Vocals can dance around the timing.

Vocals should dance around the timing - that's what's called a performance :-)
 
and when out of tune it's called character ;-)