I have to agree with the comment on aesthetics - I was happy to go for the SL4 Pro "black / neon red" frameset instead of the S-Works simply because I liked the paint job on the Pro so much more. Now I'm even happier about the decision because I've learnt the other differences are extremely minor and the weight difference is under 100 grams. Plus, my complete build with pedals and two bottle cages came to just under the 6.8 kg UCI limit, which is even better than I was expecting
Regarding the color, the images on the Specialized website definitely don't do it justice (http://www.specialized.com/us/en/bc/SBCProduct.jsp?spid=61558&scid=1101&scname=Road
) - they make the red stripes look far too orange, and some other online images I've seen make it look slightly pink, which is totally wrong. It is really a very glowing red (hence the moniker of neon red). The image of it on a shop's showroom floor towards the bottom of the following page is the only one that gives a reasonably accurate rendition: http://sparkbrs.com/archives/3581
If I had not seen one of these frames in real life at Eurobike then I would have never been interested in this color scheme. Don't make a decision until you've since it yourself. Also, the grey-on-black specialized logo makes it nicely understated, which is important to me.
PS: Try not to be a hater for someone choosing a frame based on aesthetics - when you know that all high-quality frames are competitively lightweight, sufficiently stiff, and have some verical compliance, then aesthetics is one of the few things that is actually truly different between the options.