Thanks for the good summary Alexban.
As you mentioned the major trap with speed reversion is when in a V/S or VNAV mode the A/P will revert to LVL CHG and then head for the MCP altitude. For a VNAV (RNP) approach in CL aircraft will head for 00000 (you must have an altitude below airfield elevation in the CL for RNP/VNAV) and close the thrust levers. For a two engine or more importantly a single engine V/S NDB or VOR approach with the MCP altitude set at MDA the F/D will lead the PF to pitch down to follow the F/D which if they are not watching the FMA modes can be destabilising.
The second smaller gotcha is that the A/T will only return you to a speed higher than 1.3 VS then return to ARM. This can and has caused confusion on the Flight Deck as to what is happening.
If crews know what to look for it really is not a problem, but it can turn ugly with an underperforming PM.
I do agree with Boeing though All On or All Off, but my employer does not pay me to fly it that way.