No I haven not changed my employer or anything, but my company was acquired by a global 50 company this year, and from next year we will have new 401k plan. Currently my 401k is in Vanguard and I am happy with them so far. One advantage with Vanguard is they have the lowest fees in the industry. If all other things are equal (in the long run, I do believe the performance of most large cap stock funds tend to converge), lower fee means better performance for investors.
(Picture from Money Magazine)
That being said, I also found some interesting things about my new 401k plan: the new funds categories by the investment regions; and the company stock.