Product review (4 stars): Not perfect, but pretty darn good
We're on our THIRD attempt at compact laundry that works for our condo.  We first bought the LG combo washer/dryer.  We must have gotten a lemon--it was really a disaster in terms of vibration.  I thought it was going to take out the whole floor!  The thing was terrifying, even though we had the service department come out to level it twice (and yes, the shipping bolts were removed!) The drying cycle also took an incredibly long time, and it smelled as if our clothes were getting cooked.  In reviews people seem to either love or hate this machine.

We replaced this with a stackable compact Bosch set, which is great, but still has some vibration.  It's WORLDS, even whole UNIVERSES better than the LG combo, but it's noticable to my downstairs neighbor.  With some loads the pans hanging from her ceiling and the paintings on her wall vibrate, and we can't figure out which load-type will cause it.  You should expect that the dryer will off-load heat into the space, but that was true of the LG as well.  I think that's the case with all non-vented condenser dryers.  The Bosch set has seemed well-made, and were it not for the slight vibration bothering our neighbor, would suit our needs perfectly as a family of 3.

We're having the Electrolux compact stackable set installed this weekend, primarily because it has a second floor noise and vibration guarantee.  I was surprised to see that it's rated the same as the Bosch set in terms of vibration by CR, though.  If it has the same level of vibration as the Bosch set, it's going back for sure.  But if it's better, out of consideration for our neighbor, we'll keep it and eat the cost.