This subject has been tossed back and forth before but IMO to become a truly accomplished keyboard musician you should try and stay away from using the transpose button in all but the most dire of circumstances.
Granted, I do use the transpose feature on occasion, like when using Midi files and trying to sing along in a Key that is comfortable to my range when the song is in a Key that is NOT conducive to my voice range. But when it comes to actually playing the keyboard, i.e. the Keys themselves - I make it a point to transpose using my own two hands.
It takes some effort to learn to do it, but the rewards are well worth it especially if you play with a Band as Al stated. Mistakes are bound to happen in a Live situation with a Band and you try to use the transpose feature. Not a pretty sight, as Al found out.
>> Want to be a run of the mill keyboard player and musician? - then use the transpose button frequently and repeatedly. Want to eventually become an accomplished and skilled keyboard player and musician? Then learn to do the transposing yourself using your own two hands and relegate the transpose buttons to all but the most dire of circumstances or in a Studio for - .eg. (special recording purposes), or when using Midi files and wanting to sing a song in a comfortable key. Other than that, learn to do the transposing yourself with your chops when actually playing the keyboard.
Besides, think of the thrill you'll get when you learn all those new Chords just waiting to be discovered!
And you'll actually be able to play them with your own two hands with a bit of practice!...
Just think of it!