Search engine friendly URL's surely help your SERPS. It is a proven fact.
By this I mean: http://www.webmasterpeers.com/this-i...-of-the-thread
In WordPress it is quite easy to do, you just need to change the permalinks and you may need a redirect plugin.
I have done the same to WMP. It was a real headache, I messed up so it took me one hour, but it is finally done. Hopefully it should help.
Have you made your URL's search engine friendly?