Layers

I use Sonar for a lot of things too yet I have no issue with either of your issues. Because the stereo/mono switch is in the inspector it is always visible as long as you have the inspector. Where in the track header it was dependent on the vertical zoom of the track to see it as well as the width of the header. I never liked layers so lanes are welcomed by me. Before they came out I wasn't sure I would like them. It turns out I like them very much. 

I find that in order to cross fade between two clips I have to collapse the lanes so that I can drag one clip over the other manually. There is too much fiddly half-automatic stuff going on when the lanes are expanded. The old system allowed me to manage the clips to my satisfaction.

i just hope cakewalk knows that they frustrate at least one person by arbitrarily changing these features without making the old functionality available as an option. I was looking into reinstalling 8.3 but it doesn't have melodyne integration.

The mono/stereo switch is less bothersome but more confounding, as you could edit the elements that were visible in track view, so that anyone who likes could easily guarantee that they never see it, but people who prefer not to display the inspector, which is generally fairly redundant by design, could see all functionality in the track view.

I can do most things in Lanes that I could in Layers, though I can't zoom them small/large enough and that's a royal pain when setting clip automation and such in Lane view as well as some tight edits where I can't see well enough even with a large monitor....
 
Other than that they're not much different to work with... Bloated space needs is big on my issues list and this one ranks at the top...
 
I believe Lanes opened up opportunities for other though so I'm glad for them... I too would have loved having both at the user's choice, but I understand the sifficulties in maintaining both...
 
Some issues are a learning curve with this, so I do know it took me a while to get used to it....
 
Now if they would only remove the zoom limitations and can forget about the problems created by this for me and work in peace! ;-)
 

Doing a fade out on one clip and a fade in on the other is more fiddly and less precise than collapsing the lanes and dragging one clip over the other.  With layers it was even more efficient - for example, I could do all my edits, leaving space on each clip for the crossfades, and then simple drag one layer over the other, automatically creating crossfades at each overlap.  I haven't found that to work well now.  In the old model, I could hover between clips on two different layers, and a crossfade cursor would appear, allowing me to crossfade two clips easily (I think it was about a 10ms crossfade).  Now, there does occasionally appear a crossfade cursor, which has some nice functionality, but it only appears sometimes and frankly I'm not sure what makes it show up.  Now, yes I could find that information out, but then I have to keep track of some computer programs temperament rather than simply choosing what clips I would like to hear when. 
 
Sure, yes, Sonar in its current incarnation can be used to make music.  I hereby merely register my continued dissatisfaction with the new system.  It's a big change to working methods which continues to cause headaches and which it seems to me is entirely unnecessary, since with the 'edit focus' menu (whatever the thing is that lets you choose between clips, midi notes, etc) it would be possible to allow the old layers functionality as an option.  The stereo/mono switch thing is even more of a headscratcher since it's not like it was hurting anyone to have the possibility of seeing it in the track view.
 
I have no use for destructively edited crossfades.
 
Thanks for listening.