Single-engine taxi after landing is normal in my company. The things to consider before shutting down an engine are weight, airfield altitude, OAT and taxiway/ramp slopes. It's a bit pointless to shut one down if you will need 40% N1 on the other to keep rolling.
edited to add: Contamination on the taxiway/ramp is a factor as well. Some years ago I taxied in at Stockholm with one shut down. We had to stop short of the stand to wait for the parking guidance to be switched on. Unbeknownst to me, the nosewheel had come to rest on a patch of ice (it was dark). When I wanted to move again, I applied power and the aircraft swung right. The nose wheel steering had no purchase on the ice; consequently there was no directional control. We shut down and were towed the last 20m.
I don't worry about CO2 emissions. It's a load of old cobblers ...
Last edited by Wingswinger; 19th Jul 2007 at 10:38.
Reason: addition