Sachsenmodelle has gone through a number of changes over the years. For a period in the 1990s, the company was in a partnership with Roco. After that partnership dissolved, Sachsenmodelle declared bankruptcy and was bought by Tillig. The cooperation with Roco led to improvements in the design of many of the models of this former East German company. Those improvements can still be seen in current models from Tillig, including the level of detail, close coupling shafts and mechanism.
Today, many of the Sachsenmodelle/Tillig HO models remain less detailed that productions from other companies (LS Models, ACME, RailTop, etc) even though a lot of production is done at the same factory (Modern Gala) in China. The Sachsenmodelle models interior details are reminiscent of models from the 1970s and lack in many cases the multicolored precision of other brands.
I was relatively impressed with the models of the SBB Heavy Schlieren coaches. They are pretty nicely rendered and can be combined with Roco and Lima coaches. I have a few DB AG (ICE livery) and DB Nachtzug coaches that I operate with Roco and LS Models coaches. The quality of the product (window inserts, interior details, decals) are better on the Roco and LS Models products. Still, as no other manufacturer has made a model of the Bimz/Bomz coaches, I decided to go for the models.
One model I am looking at with particular interest is the newly announced SBB Zurich S-Bahn doubledeck coaches. Sachsenmodelle already had a model of the second class coach. This year, they will be making the combined first/second class coach and the pilot coach. I have the Hag Re 450 so this should make an interesting consist. The modernized coaches with the red doors and the VBZ lettering will match the new Re 420 "LION" announced by Hag.
As far as operation, I have not noticed any problems with operation on C- or K-Track. The long double deck coaches may have issues with Maerklin switch tracks (lantern). I will have to test one coach before deciding on whether to order the entire consist.

Regards

Mike C

The S-Bahn Zuerich models are Sachsenmodelle/Tillig. The Hobbytrade models are DB Regio Doubledeck coaches that were tested by the BLS in 2010. You can read about the Sachsenmodelle models here:
http://www.eyro.ch/downl...s/news12/tillig_2012.pdf (see Page 13).

Here is a photo of such a consist with a Re 450: http://www.railfaneurope...tettbach/sbb19990114.JPG

Here is a photo of a new consist with the modified Re 4/4II (Re 420) "LION": http://www.railfaneurope..._85_4_420_230-5_chur.jpg

Reduced length (1/9X scale) models are available from Fleischmann

Regards

Mike C