The ergonomic/natural/arc keyboards are, by far, the best products Microsoft ever sold. I do love the Apple trackpads, however. There is no better way to work on a Mac.
As for my Linuxing, I have a Unicomp "Battleship" (PC122 keyboard) that's loud as hell, but has the best feel since the beam spring keyboards God added to the IBM 3270's when it made them in the 6th day.
I'm still rockin' the original Microsoft Natural on my workstation. My current motherboard has a PS2 keyboard connector, but I have a USB-PS2 adapter if/when the day comes to upgrade.
I originally bought three of them, and two are still working good.
I also recently bought one of the new Microsoft keyboards, and the feel on it is still pretty good.
Trackball is way better than any trackpad for me. I have three Microsoft Ergonomic keyboards. Two of the Surface ones and one of their cheaper ones which is about $20 at a BestBuy.
The thing with the trackpad on Macs is the gesture thing. Swiping desktops, zooming out on all windows, the "3D" click... The fluid way it allows me to work is priceless.
As for my Linuxing, I have a Unicomp "Battleship" (PC122 keyboard) that's loud as hell, but has the best feel since the beam spring keyboards God added to the IBM 3270's when it made them in the 6th day.