I tried Motherhood first, and agree that their return policies are terrible -- particularly since almost every item I got there was defective!
Old Navy and Gap were a bust for me, it was all so thin, badly cut, badly proportioned ... it just looked cheap.
Target was my saving grace. I was hitting maternity size during the winter and especially needed jeans that looked more classy (i.e. not the tight thigh thing). Their boot cut and trouser jeans were good. Not fantastic but hitting them with an iron keeps them looking pretty good.
And their tops were very long, with some fun prints. I LOVE LOVE LOVE the Liz Lange scoop neck T-shirt. It is indeed a true short sleeved T-shirt, I'm just disappointed it doesn't come in many colors. I'd avoid their T-shirts that are folded on the shelf, they are WAY too thin and lose their shape fast. But the V-neck empire waist styles were flattering on me from the "I'm not fat, I'm pregnant" stage to now ("very very due").
The other biggie was camisoles from Costco. They weren't maternity, just regular Cotton-Modal camis in bright colors, in a 2-pack. The large fit me just right and I'm a 16, bra size 38F. I'm sure the XL would be fine on a size 18-20 woman. They're pretty long, and mixing the colors under the Target V-necks brightened everything up. Plus it was cheap to get 8 different colors. (Most maternity camis come in a few colors and they're expensive).
I am loving Target's maternity dresses this week (modal ones, not poly - the poly I sweat in and stink!). I'm so huge I can hardly dress myself, and it's getting hot here this week. Even at 80 degrees I'm OK with the long sleeves and now that their spring stuff is out I'm sure they have short.
My guy helped too ... all his favorites come from the Target stuff.
Lane Bryant was good for bras (maternity bras are a waste, it's too early to get nursing ones, and Motherhood bras are expensive and crappy). I'm sad they don't have nursing bras, even the expensive G/H-cup nursing bras I found at Nordstrom aren't nearly as nice a bra as the Cacique. Some bra strap extenders (from a sewing store, not a department store - the price difference is huge) were very important once baby got high enough to expand my rib cage.
I wasn't sorry Lane Bryant didn't have maternity -- so much of their stuff now is synthetic fibers, which to me at least are uncomfortable even while not pregnant. I notice a lot of women don't notice, body odor gets strong fast in synthetics, and in the summer you're going to need breathable fabrics.
(also my complaint about Target jeans - the thick poly tops - here Motherhood's "Secret Fit Belly" in a straight leg or boot cut were a little more comfy even though on every single pair, the fabric unhemmed and unraveled at the top).
And did anyone mention to you, tucking the top of the stretchy tube into the bottom of your bra keeps the maternity pants up? I wish I'd known that sooner!
And get some pretty scarves ... those you don't need a maternity size!