, I share many of your concerns with the Antec cases in question. I also own a Solo (not currently used) and an Antec server case that is several years old but still very solid. I've also handled and used several other products of theirs over the years, so I'm (hopefully) not making silly commments.
It's hard for any company to please everyone with a single product. That's why companies use market segmentation to differentiate their lines with increasing price scales. For computer hardware like cases, it's somewhat harder to do this, plus they have no compelling reason to want to satisfy every users' wishes and provide several versions of the same product as you would find in cars for example. Seeing that the percentage of the population who buy cars is large and the percentage who buy specialist PC cases is quite small, we can probably understand this from an economical perspective.
Despite the wishes and complaints of SPCRians over the years with regards to their products, Antec will pursue their own roads with or without our approval. The P18x has sold truckloads for them. I don't know what the figures are, but I suspect that the P18x line does much better for them than the P150/Solo/Sonata line. Unless people vote with their wallets and avoid them, they will feel they have no reason to come up with anything drastically different. It's a good enough design for them without offending many but pleasing the majority who will overlook its shortcomings in favour of functionality and long term ownership. Sounds like a Toyota, doesn't it?
Almost forgot, I am not so enamored with the vertical hdd situation. I have all SSD's in my computer, three of them, and I don't know if vertical installation is an issue or not.
MikeC already dismissed this in the article thread on the P182SE
a couple years back. I think modern drives should be fine installed vertically. Not sure of the situation with SSDs though as I haven't jumped on that wagon yet. But because of my obsessive nature, I always install my drives horizontally. Even with my external drives as I just feel more at ease with them this way.