This year I've decided to go with nylon slings for trad climbing. I bought some Black Diamond nylon runners which are cheap and will do the job fine. What I had been using previously were the "shoestring" Mammut 8mm slings. These are the ones that everyone has, and there's a good reason, they are very light, compact, and strong. I had 16 of them which I wanted to see if I could sell. I tried asking around and nobody wanted them. It turns out people don't like to buy used climbing gear. So I put them on ebay and sold them all in one day.
1. cheap as hell
2. much better elastic properties
3. the ability to tie knots and connect slings with hitches
4. can substitute for cord when making friction knots (kleimheist and autoblock)
In my mind the pros far outweigh the cons. For most trad climbs I only carry 4-8 slings so it was a pretty minimal weight gain.
Here is what DMM says about Nylon vs Spectra.