I just came across your posting and had to reply. :-)
I've been playing sax for 14 years now and just finished a BA music performance degree and I think it's great that young players like yourself are actually taking note of the sax [no pun intended], it's capabilities and what it can bring to an ensemble. Whether or not the composer 'knows' the saxophone can have a drastic effect on the color and mood of the piece. As far the technicality, I've found that an advanced saxophone player can play fast and complex runs on the same level as a flute or clarinet if not better because we don't have to worry as much about crossing the break or losing our volume/pitch the higher or lower we go. If you really want a dark, dramatic effect, try combining all of the reeds together in their low registers. Similarly, you can create a good woodwind scream with flutes and clarinets, but if you add saxes to the mix [at about an alt. A or B] it can make a sound that will cut through the band like a hot knife through butter.
Unfortunately though, there are many "experienced" composers out there that think you write for a saxophone by taking the clarinet's part or lowbrass' part and clicking the Transpose button. I've even seen sax parts that have notes below a low A that a sax can't even play--which is clearly a case of the composer taking the bassoon or a low brass part and transposing it and not even bothering to double check the part afterwards.
