Almost 50% of all L1 petitions get RFE (Request for evidence). It's becoming harder to use this visa to bring people to the US these days, too. It's especially difficult for big outsourcing companies (proving and supplying enough evidence for the "specialized knowledge" (L1B) category is really non trivial for the companies and often not clearly understood by the USCIS officers, hence the RFE).

However, USCIS has recently released a new L1B adjudications policy for public feedback (http://www.uscis.gov/news/uscis-posts-updated-l-1b-adjudicat...) where they clearly define the "specialized knowledge" category. Maybe this will help companies to properly understand what's needed to demonstrate the specialized knowledge in the future, but I really doubt it.

L-1 visa holders can't change job.