Does anyone know if there are any cons to the friction change?

 

The main issue is takeoff/landing performance, which may be marginally affected (i.e. shorter takeoff roll/longer landing roll) -- however, as the Dynamic Friction modification only operates below 30kt (IIRC) the effect should be minimal.

 

I haven't noticed any negative effects in all the time I've been using it, which is a long time!

How will this work with engine cool down/warm up times?

 

They can either start their engines on the way to the end of  the taxi or  at the disconnecting  area  and  visa  versa on the way back  to the gate

http://www.taxibot-international.com/#!try-taxibot/c1mbf

I did a short single-engine taxi yesterday at Chicago, but I started it shortly after I got on the taxiway, ground just wanted to me to get moving so I decided to start the engine while moving instead of stopped on the taxiway. Also the air Canada q-300 do single engine taxis at PDX and I believe there Q-400 do the same although Canada's Q 400s don't come to PDX. QXE doesn't perform single inch and taxis their Q-400s

Yeah, I don't think the same concerns for single engine taxi are on the Q300- the Q400, only because of the drastically longer fuselage has some issues, since the "arm" length between engine and nose gear is so long. In the Saab 340 we taxied single engine all the time, or at least with one in feather. That is, if the weather allowed.

Here in NZ I have been on many regional flights on ATR72 and Q300 where the crew shuts down the left engine on the runway or during taxi-in. By the time we park, it is pretty much stopped. That way ground crew can head straight to the plane to save a bit of time, Air NZ turns are pretty short on these sectors.

Should note that there is a difference on the Dash vs. Having one engine feathered and taxing and one engine shut down. Some operators do either/both or neither.

 

Single-engine taxing on the Q is relatively new (only in the last year or so). You do lose some redundancy for the brakes though so some operators are still a bit leary about it.

 

 

Here in NZ I have been on many regional flights on ATR72 and Q300

 

This is an apples to oranges comparison.  The ATR72 taxied well on one engine but it is also about 1/3 the weight of a 737-800.  You really can't put the two operations in the same category.