Thinking of replacing my Bat spaceheater with class D, real world thoughts please

It comes down to personal preference.  I have had experiences with different Class D configurations.  I also build my own components.  In all of my testing and listening over the years, I am able to identify what sounds like what, sometimes a disadvantage because I listen to equipment versus music.  Anyway, you have to hear what works in your system.  Just because I do not prefer Class D does not mean that you won't be satisfied with  them especially for the price.  There are advantages and disadvantages to all components but your budget and your taste is what really matters.  Happy Listening.

The only way to be satisfied with the end result will be to try the amps in your own system and compare them directly with your BAT.  I suggest you listen closely and objectively since, in my experience, the results may not be a night and day difference, but rather one or the other may be better at certain things.  Be prepared for the Class D to be much quieter but I wouldn't get overly hung up on that benefit.  Compare note development and soundstage between the two and listen for fatal (i.e., dealbreaker) type issues that you just cannot live with long term.
If you want to try NC1200, I think I know who to contact so you can audition a pair in your system.  Some Class D amps you may need to actually purchase and then have a 30-day "return" period, with or without restocking fees.  Small price to pay IMO to get what you want, or to not make a big mistake.
Since you are so curious, I suggest deciding how much you want to spend, and then asking the folks here for Class D amp suggestions in your price range and then contacting those manufacturers to try and set up an audition.  BTW, they are mostly easy to ship and some come in flight cases which would make it very hard to damage them.  It sounds like you are at the point where you need to hear some for yourself in your own system.

I entirely agree that it will all depend on how it sounds in my system and am prepared to do a number of a/b comparisons of a lengthy nature.

However my main focus was to see how many had actually gone this route and if they regretted it and just some general views on the many class d amps out there.

Ones I had considered so far include Bel Canto, Jeff Rowland, NuForce, D-Sonic to name a few.
All claim to make prodigous power from a small box up to 1500 watts in some cases, although we all know numbers on their own do not mean a great deal.

I don't see Ncore on your list but Rowland uses NC1200 amplifier modules in its upper end amps and BelCanto also uses Ncore - custom modules in the Black, and Ncore NC500 modules in the REF 600M, which has received all the rave reviews.  Acoustic Imagery offers a bare-bones pair of NC500 monoblocks for $2K - for the pair.
Between Rowland, Bel Canto and D-Sonic, you certainly have the price range covered.

I wish you all the luck iberwaltz.  I tried to get rid of my VTL space heaters a few years back. I used Classe and Bryston for a few months each and always went back to those room heating tubes. I gave up and later upgraded in the VTL line.