IMHO, unless you're playing sessions where you HAVE to cold sight read to make a living and ASSUMING you have an excellent memory...I would learn to sight read well enough to figure out a new song and then play it from memory.

We've all seen world class pianists play long and complex piano concertos from memory so certainly, there is nothing "unprofessional" about doing so.

So, assuming your are basically an "average" player...I would personally advise focussing your time on the huge array of issues necessary to play very well before worrying too much about sight reading.

QUALIFYING NOTE: I can play any song on a piano as long it is one of the two that I know and as long as they are in the key of C. (-:

But I've been around brilliant pro musicians, including keyboard players... for a LONG time and many of them don't read AT ALL.

NO disrespect to great readers!!!! I'm just saying that you can PLAY fabulously if you don't read but cannot play fabulously because you CAN read.

Just my 2 cents.

Jim