Now for a little practical experience instead of theory...

I started out using a sled when I first got my saw.  I didn't have a miter gauge and it was the best way for me to get accurate cuts.  Then, like Ryan, I got my Incra miter gauge and shortly after decided I was tired of storing my sled and to the dump it went.  So my general methods have changed and there are times I have wished I still had the sled like for really small or really large pieces.  But I haven't ever wished hard enough I wanted to store another one.  I will say that the sled stayed really accurate for several years.  I built adjustability into my fence when I made it because that's what always seems to go bad for me with wood jigs, the squareness.