I have a total of four sets as you have described, back to back in my layout.
I have not had many problems at all with them, and it is a very common configuration for simple layouts..
However, if you run very short engines, with two rollers that are really close together, you can get a stall. One cause is the two rollers simultaneously being on dead center rail sections, and the other cause is that as the little engine rattles and jumps over the connections and frogs, one of the outside wheels on the hot outer rail can rise above the track, just a hair, and bring the engine to a stop.
For a novice like me, the first problem can't be cured (except by lashing a car behind the engine and having a roller on it for the center rail), but the second problem can be cured by removing the rubber tires on the engine and also meticulously leveling the track (which is not easy to do with back to back switches.)
If you try to run an old engine with just one roller underneath for the center rail, then you may be in for incurable stalls.
An annoying factor is the noise and jumping as small engines pass over the two switches, and the momentary "flashing" on an off of any light accessory in a car that has a single roller.
If you can avoid the configuration without totally gutting your layout, I would recommend that you do it. Even adding a two- inch straight section between the two switches may help. If you can't, then avoid getting really small engines, and learn to ignore the rattling and flashing (as we did when we were kids.)
I have never run huge engines on my layout, like Big Boys, but others have said these will create big problems for you.
Mannyrock
If you run a very short engine, with
