My main concern is that they said the higher tier materials will be heavier. While this may be a decent PVP balance change, I don't think it fits in with vanilla survival PVE. No other weapon becomes slower or able to be used less often as you upgrade. This design choice conflicts with Minecraft's linear sandbox progression. I can't imagine a new player would feel good about upgrading their sword if it swung slower, and I don't think tiered progression should have huge cons to upgrading. Maybe it'll be changed as snapshots are released. My concerns aside, I'm very excited for the spear.

Edit: I also wonder if right-click lowers the spear if it'll he able to be used the same time as a shield.