I don't have any stake in TruePianos or their sales, but I thought Sonar owners looking to move on to other DAW's might appreciate this.  This was mentioned in another thread, but I am providing additional clarity based on my experience.
 
http://www.truepianos.com/cakewalk.php
 
The above link is not new... (30% off for Cakewalk customers), but what IS new is an additional 40% off sale on the full version of TruePianos for the remainder of 2017.   So... those discounts are stackable... 40% off public deal + 30% off for Cakewalk customers, you can get the full version of TruePianos for under $50 (US).  I believe the deal for non-US is also equally attractive.
For anyone who might miss TruePianos after moving away from Sonar, I think this is worth a look.
 
NOTE: The form that requests the cakewalk serial seems to only work on older serial numbers CWSP-x.xx...., I used one of my older serials from my cakewalk products page and it worked.  In a support email I sent to Truepianos tech support, it seems they are trying to expose another link that will work with newer serial numbers.  In any case, their FAQ says to contact their tech support to get the discount if your current Cakewalk serial number is not working with the discount page.
 
Editorial:
As I consider moving away from Sonar, I do believe I would miss the TruePianos module.   (Though I've heard in the "piano-modeling" area that Pianoteq is the one to beat, it's much more expensive and IMO TruePianos is no slouch.)  I asked TruePianos tech support if they would consider "giving away" the Amber license to Cakewalk customers, but it does not sound like their contractual or license management system would make that very feasible.  So... if you appreciate the TruePianos module you've had in Sonar, I think their current offer is a good deal to keep it in your new DAW adventures.

I tried my SPLAT serial number (no joy), my Sonar 8 Studio serial (no joy), my Producer 4 (no joy)
Does it work only with Producer versions over 6.0? Not even Platinum?

I believe the discount should work for any version of SONAR which included the TruePiano plug-in. Email them if you are having trouble getting the discount.

Thanks scook... I clarified my original post that the Cakewalk deal is probably only valid for versions of SONAR that included TruePianos (SPLAT qualifies, of course). Regardless, the non-Cakewalk price is still pretty good.  See later post, it seems TruePianos is being pretty flexible on this discount.
 
Their FAQ clearly states that their Cakewalk serial number checker is not up to date, so contact them if your SONAR version is eligible but your serial is not recognized.  I suspect they will work with you.  When I contacted their tech support via their web page, it was responded over night by email.  I'm not sure where they are located, but give them some time to respond. Good luck.

Personally I'm not about to hand out my serial number to anyone. 
 
And for that price you can wait until the Air expand pack goes on sale or even purchase the Air Mini Grand individually. After getting the Mini Grand I can no longer listen to True Pianos, I've swapped it out f every project now. 
 
And besides , if you have one of the older versions of Sonar, just do a bare bones install and there you go= You'll have true Piano free. 

That's a great deal - better than any previous sale price - whether you're moving to another DAW or not.
 
As many know, Amber, the subset of TruePianos that we got bundled with SONAR, is the weakest of the four piano models. I don't care for it and have never used it. But reports indicate that the other models are better.
 
In any case, the benefit of TruePianos isn't that it sounds great but that it's a modeled synth rather than a sample library, and therefore much lighter-weight than any Kontakt instrument. Don't judge it as a solo piano, but rather how it would work in a supporting role as a rhythmic element in a larger mix.
 
Now my question: has anyone actually bought the product for 50 bucks?

Cactus Music
After getting the Mini Grand I can no longer listen to True Pianos, I've swapped it out f every project now. 
 
And besides , if you have one of the older versions of Sonar, just do a bare bones install and there you go= You'll have true Piano free. 

I guess you are comparing the Mini Grand to TruePianos Amber (the one bundled with SONAR). There are 6 pianos included in the full version.

Cactus Music
Personally I'm not about to hand out my serial number to anyone. 
 

I questioned this too with the overloud unlocking, but it seems everyone is happy to d so with them

bitflipper
 
Now my question: has anyone actually bought the product for 50 bucks?

I paid $88 in 2013.

Cactus Music
Personally I'm not about to hand out my serial number to anyone. 
 
And for that price you can wait until the Air expand pack goes on sale or even purchase the Air Mini Grand individually. After getting the Mini Grand I can no longer listen to True Pianos, I've swapped it out f every project now. 
 
And besides , if you have one of the older versions of Sonar, just do a bare bones install and there you go= You'll have true Piano free. 

We regularly hand over credit card numbers and other personal info to one man operations in former eastern block countries regularly. Your sonar serial is not exactly a hot commodity right now and is among the least likely things to be used for nefarious purposes out of all the info you give. Serials for a dead product are somewhat worthless to everyone except people like us who already own it.