I believe you are referring to JONA (his location I think is Sussex) -- yes when he answers fruit tree questions, I always learn something.
Most of my fruit trees are from on-line sources but not from the one OP mentioned, so it's informative to hear the negative experiences from another member (sorry that happened to you though).
I've had few negative experiences -- and don't order from them any more -- and many positive experiences -- and stick with them now. One early lesson learned is that no matter how unique the variety, it's better NOT to order from geographically distant main order sources unless I'm willing to pay for extra service shipping. Good service mail order sources located within closer distance can sometimes actually ship/deliver in shorter time than stated for standard delivery.
No matter how good the on-line source is and quality of their nursery stock, the plants can get pretty stressed out during the shipping process, so speedy order turnaround, good packaging, and short shipping distance/time spent in the package all influence their condition upon arrival. Time of the year and weather conditions come into play. And make sure to provide instructions for the carrier about WHERE to leave the package. (I ask for the package to be left in the shade/protected location).
Also, I order plants that need extra winter hardiness from nurseries in lower USDA zones, and plants that need extra summer heat tolerance from sources in higher USDA zones. You'll notice that hardiness range listed may vary accordingly as well and make sure that your location doesn't fall out of range in either end. (For example, Fedco in Maine has apple trees that are listed for Zones 3-6. I wouldn't get those since I'm in Zone 6 and want at least one zone level buffer. But I might get a fig tree if they said they have one that's hardy to Zone 5)
You also have to keep in mind that depending on location, their trees would have gone dormant earlier in fall or haven't gone dormant yet when your ground has frozen, or, in late winter/early spring, their trees are ready to come out of dormancy when your ground is still frozen or it's way past time to plant in your garden and they are just getting ready to dig. Shipping weather is affected similarly as well. I'm not sure if I would trust shipping routes that have to cross the Rockies (for example) or desert conditions that significantly alter the temperature they started and will end in.
Most good mail order nurseries that have been doing this for a long time will know what they are doing, and will know even better than you what the best time to ship to arrive in your garden will be. But when in doubt, be sure to contact them and make appropriate arrangements.
There is a greenhouse nursery that offers to add hot packs in the package during freezing weather and cold packs during the summer heat if you pay for express shipping. It's a bit of a conundrum since the plants would need the hot/cold packs more when it takes longer to deliver, but there it is. -- unless it's a gift or something that absolutely must be obtained "off season" (or maybe they are having a terrific sale that offsets the cost of expensive express shipping) -- I consider my plant material mail order windows to be dormant season in my garden for dormant plants, and frost-free and heat wave-free seasons for leafed plants.