I actually asked a simillar question couple months ago and some of TI Folks didn't recommend OnQ as above links show. So I was fully aware of that when I was selecting a lender. However, I ended up choosing OnQ and I'm actually closed with OnQ today, so let me share my experience with them.
I started loan shoppings approximately 3 month before COE, and my final candidates were OnQ and Wellsfargo. Many guys here recommended Wellsfargo and their rate was better than OnQ as TI folks said. At that time, the only reason I considered OnQ was they are builder's preferred lender and they guaranteed no-late-closing penalty even if delay is cuased by myself. And they gave me a written confirmation that my rate lock is guarantted until closing. On the other hand, Wellsfargo offered me .125 point charge for 15 days lock extension if my COE is delayed and 60 days lock period is over.
At that time I was about going with Wellsfargo due to their lower rate. However, when I told OnQ that I decided going with another lender, they asked me the reason and I said Wells offered me lower rate. Then they said, they can match not only Wellsfargo's but also any other lender's rate if I can show them other lender's written quotes. When you do a mortage shopping, lenders normally don't give you written quotes so it wasn't realistic offer but when I just showed them my email that contained wellsfargo's rate, they offered me the same rate as Wellsfargo's.
Once I lock the rate of OnQ's 30 years fixed product, right next day, I changed my mind and regreted I chose 30 years fixed product. I wasn't expecting that I could change the product after lock but when I asked, they withrawed previous rate lock and allowed me changing to ARM without any cost and even lower rate than previous day. (It also matched Wellsfargo's rate)
My cons for OnQ was, when I wanted to get a daily rate update, sometimes it was hard to reach their vice president guy because he was usually busy dealing with other customers and meetings. So most of time when I called him, I had to leave memo and he contacted me a few hours later. However, he never missed any response. Their vice president guy was a smooth talker and very professional, so I had no trouble talking with him.
Unlike other member's previous experience with OnQ, I had no complaint after rate lock. Everything was smooth and other staffs were very responsive. Even when I asked/requested something by email, their response was usually very quick (normally within 1 hour). They did a mistake just 3 days before COE, so I had to re-sign their loan documents but it didn't cause any delay on my closing date. So over all it was a very smooth and stress-free transaction with them.
Wellsfargo seemed to be good though. they had my own loan manager and it seems they have more staffs for my case, so communication wise they may provide better service than small lenders. Apart from interest rate, their other charges were a little more expensive than OnQ and their home insurance quote was fairly expensive. Of course, OnQ doesn't have their own home insurance provider, so I was free to choose my own.