Combining "Buy a portable computer instead" and "The only peripheral you absolutely need is a hard disk or network drive to put backups on" doesn't make sense. I don't know about you, but my productivity tanks the second I don't have a mouse.
Use the mouse for what it's good at: pointing at things and selecting text. Use the keyboard for what it's good at: entering text, such as regular expressions to transform the code you just highlighted.
Incremental search, dude.
On the Mac, the latest gens of their trackpads have obsoleted mice for me.