Ease of decoder programming, what’s that you ask?
You put a decoder in a loco to get it to run on DCC. Decoders cost from $15-$20 for a basic decoder, to $35-$50 for a fancy decoder, all the way up to $75-$150 for a decoder that does sound.
Once you have a decoder in your loco, you need to set it up with the options you want, tune the loco performance (slow start, top speed, braking delay, how you want the lights to work [regular, rotating beacon, gyralight, etc.], things like that). This decoder setup is called programming the decoder, and you put values into special “configuration variables” in the decoder, called CVs.
Without a computer interface, you can program CVs with your DCC system, but if you want anything but the most basic settings, you may need to study the decoder manual carefully to figure out what CVs do what, and what binary value settings turn what feature on and off.
With a computer interface and a PC, you don’t have to know a lot about CVs and binary settings, you can just point and click options with a mouse on your PC to adjust the settings in your loco decoders. If you expect to “tweak” with your loco settings a lot (speed matching with speed curves for consisting, and so on), I consider having a computer interface a must so you can easily and quickly tune your loco decoders.
Basic programming of CVs with the keypad that comes with any DCC system is fine, but more advanced loco tuning is a lot easier with a PC hooked to your system.
I have an extensive FORUM CLINIC I’m doing on here that gets into more of the details of setting up and using a DCC system. Once you know some of the DCC basics (I don’t really cover those in my forum) then you can read the forum and probably learn useful things about how to make DCC work best for you. See: http://www.trains.com/community/forum/topic.asp?TOPIC_ID=36389