We've dealt with Washington Mutual on about 4 house loans and they've been decent. However, I'm inclined to say your results are more dependant on the expertise of the person you deal with rather than the company. YMMV. BTW, I've heard some horror stories about WA Mutual as well.
It reminds me of buying a PC in that regardless of which brand you choose, somebody is going to pop-up and tell you some horror story about whatever your choice is.
One thing does seem consistent though: The "front" companies that initiate a loan and then simply sell it off are not as desirable. While I think just about all mortgage companies can do this, some tend to do it more than others. You might ask prospective lenders about this. We've never had a loan sold-off by WA Mutual...at least that we know of.
You might also check-out how well equipped the mortgage company is in terms of online presence. You may find it useful to occasionally check your loan balance or nab tax docs via a website or see if your last payment was received, etc.
You are smart to avoid that ripoff mortgage insurance, IMO. Of course, remember to save all your paperwork as "points" you pay for the loan are probably going to be tax deductions for you. You may also wish to pay your property taxes yourself. Since your putting 20% down, your mort. company should have no problem with that. You might as well be getting interest on that money.