I held Vanguard GNMA in my Schwab account for several years, but they didn't allow Admiral share conversions. Two+ years ago I finally got the bright to move the money over to Vanguard. The process was pretty smooth the shares got transfered in kind to Vanguard. Vanguard converted them to Admiral shares, and avoid paying even the modest capital gains that would have occurred with sales and repurchase at Vanguard.
I figure it saves me a couple hundred each year in fees, well worth the small amount of trouble.
I expect that I'll be moving more money to Vanguard in the coming years, because when you factor everything in generally admiral funds are cheaper than ETFs. I still am a big fan of Schwab service the commissions are down $8.95 and are often cheaper for things like bonds and options than most other name discount brokerages.
Unfortunately,Schwab's mutual funds which used be merely mediocre have really gone down hill. For example the Schwab Yield Plus fund (ultra short term bond fund) has just collapse the last year, and its Morningstar rating has plummeted from 5* to 1* as its NAV has dropped from 9.60 to 6.60...