I used the website Dave's Garden to research mail order places and felt confident choosing a reputable place -- in the end I used 4 different mail order nurseries for 11 shrubs and 1 tree.
So how do i feel about mail order? Point blank: If instant gratification is your thing, don't do mail order! Oh my god some of these shrubs were tiny. Almost laughable!
I ordered some dwarf Korean spice viburnums and they came so small a hand spade (or my thumb) could dig the hole. Perennials from the arboretum sale were harder to plant. Oh well. I will enjoy watching them grow as I grow old.
Can you spot the tiny viburnums??
On the other hand, I ordered a tree (Dwarf River Birch 'Fox Valley') mail order and it came larger than I imagined. You never know what you will get.
So far, my mail order plants that I planted last fall (Nikko deutzias and virginia sweetspire) have survived the winter... and the rabbits! They are still small in size (mostly because 'ol cotton tail nibbled them down) but I'm eager to see how they grow in their first season.