Though I'll agree that this is a convenient stop gap solution, remember that when you simply hit the transpose button & play everything in C, you can't always acheive the same sound as actually playing (physically) in another key. Why? Because the physical layout of the raised black & white keys limit your chord voicing choices available in one key, but not in another.

In addition, certain songs & styles (ei: the blues) are more effectively played (on the keyboard) in specific keys which allow your finger to more easily 'slide' off the black (blue notes: b9, b3, b5, #5, b7) to the neighboring white key. Try playing a blues riff in 'F', and then 'E' and you'll quickly feel & hear the difference.

The bottom line: Though it's convenient to transpose to C, just don't let it become an 'end all' crutch. Learn to develop proficiecy playing in all 12 keys (or at least the other more commonly played ones: G - C - F - Bb - Eb - Ab). Both your musicianship & artistry will benefit as a result.

Note: Surprising as it may seem, playing in the key of C# or F# (from an ergonomic hand position standpoint) is actually a lot easier than C, as the position of the raised black keys better matches the contour (shape) of your hand.

Scott