Maybe a 'Newport' would be better there.

To understand a little more about the 'expected' problems with this plant, be sure you avoid the typical catalog description. Thundercloud and other flowering plums are pretty infamous for being prone to a wide variety of disease and insect pests. If you live in an area where Japanese Beetles are a problem, your tree will be the neighborhood magnet.

My neighbor has a purple-leaved flowering plum (don't know which one), and though we much admire the spring floral display, I'd say for about 9 months out of the year, the tree looks pretty ratty (between the beetles and the powdery mildew and tent caterpillars.)

I'm thinking that bboy knows something about 'Newport', in particular, that makes it a better choice for you. What's the story on that, bboy?

Hybrid developed in Minnesota. Hardier, tougher and more elegant than purpleleaf cherry plums like 'Thundercloud' and 'Krauter's Vesuvius', both originating in California. When we had a cold winter (2F-12F in different parts of Seattle) here in 1990 many of the purpleleaf cherry plums actually had large sections of their canopies freeze and die; damage dating to then still quite visible.

Maybe I'll explore my other choice, the Eastern Redbud. At least that one is native to my area and might be less prone to pests. I have yet to see a Japanese Beetle in my area, so I don't want to break wasn't isn't broken.

I live in Southern CT two miles from LI Sound and 2 or 3 years ago planted four plum trees, two of them Thundercloud on the front of my property - which faces north. They have done fine and there have been no insect problems - japanese beetles were not a problem for those trees last summer even though they ate up my kitchen garden plants. One plum tree in the back of my property, not a Thundercloud, was stripped up by deer which killed a major side branch - they also tore up the bark on my clump birch but those trees with at least 50% of their bark remaining have survived.
This spring the flowers on the plums, any variety, were not as abundant as they were last spring.....I dont know what the reason for that might be. What affects flower density?

The major question I have is how much pruning, if any, these Thunderclouds need. They are now growing well with longish branches - what were $40 trees from HD are now $300 size trees (if bought from a nursery). Do they need pruing as much as say Kwazan Cherries?

2 or 3 years is normally not an adequate interval to establish reliability. If you happened to have record cold during that brief period and the trees sustained no damage that would be illustrative.

Japanese cherries such as 'Kwanzan' should not be pruned much. Established purpleleaf cherry plums (like 'Thundercloud') can be lopped if desired to produce long whips lined with flowers. Specimens so handled will not have relaxed, natural shapes. Pruning out of dead twigs on those allowed to develop normally can be expected to be needed to maintain a tidy appearance, as with Japanese maples these tend to build them up on the interior. And as mentioned earlier frost damage may result in large areas of dead branches.

bboy, we had a couple of really cold high wind periods this winter (which otherwise was mild given my oil consumption as a measure!) which burned the heck out of my skip laurels and to some extent the rhodies - but the plum trees were unaffected (other than one of them by deer). So thats a good omen I guess.
Do you think there is any quality difference in trees sold by HD compared to nurseries? I guess thats too general a question.