What bothers me is the inability to buy a USB multitouch trackpad. I've only seen one model for sale, only in Japan, and lacking Mac drivers.
You can pick them up on ebay but they're now quite old and extremely expensive.
Many modern touchpads support multitouch in hardware but it's disabled in drivers [1].
I believe it has something to do with Apple sitting on multitouch patents. Even Android phones were supposed not to have multitouch because of Apple.
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[1] For example Synaptics ones in Thinkpads. You can get multitouch using modded drivers.