I totally agree. The new Mac Pro is plenty expandable, the expansion just happens on the outside.
I've had two Mac Pros so far. They're great, and I love the internal expansion... in theory. In practice, they never got any PCI cards beyond the graphics cards that came with them, and I used the hard drive bays more because I could than because I really needed it (e.g. keeping the old drive in the machine when upgrading storage and using it for secondary stuff).
About the only problem will be GPU upgrades a few years down the line. TB2 is not quite fast enough to make that a good option. But most Mac Pro owners don't upgrade that, and it's plenty good for storage and other PCI cards.
I've had two Mac Pros so far. They're great, and I love the internal expansion... in theory. In practice, they never got any PCI cards beyond the graphics cards that came with them, and I used the hard drive bays more because I could than because I really needed it (e.g. keeping the old drive in the machine when upgrading storage and using it for secondary stuff).
About the only problem will be GPU upgrades a few years down the line. TB2 is not quite fast enough to make that a good option. But most Mac Pro owners don't upgrade that, and it's plenty good for storage and other PCI cards.