Hey PartTime,
I really see nothing compelling to do the move, at least not like your hair is on fire. I had just north of $100k in an IRA with TIAA-CREF that I did roll over to Vanguard, and glad I did. Overall fee structure was a lot better, and it got me to Flagship status with Vanguard.
Now, if it were like I see with some folks who have ridiculous high cost options (Index 500 funds pegged at 1.35% ER), then yeah, I would be singing another tune. I do have to wonder, would you even get that good of an ER with Vanguard, for a similar target dated fund, investing under $10k (non-admiral shares)?
Good luck.