Eliezer, I'm with you that a properly designed mind will be great, but mere uploads will still be much more awesome than normal humans on fast forward.

Without hacking on how your mind fundamentally works, it seems pretty likely that being software would allow a better interface with other software than mouse, keyboard and display does now. Hacking on just the interface would (it seems to me) lead to improvements in mental capability beyond mere speed. This sounds like mind hacking to me (software enhancing a software mind will likely lead to blurry edges around which part we call "the mind"), and seems pretty safe.

Some (pretty safe*) cognitive enhancements:

• Unmodified humans using larger displays are better at many tasks than humans using small displays (somewhat fluffy pdf research). It'll be pretty surprising if being software doesn't allow a better visual interface than a 30" screen.
• Unmodified humans who can touch-type spend less time and attention on the mechanics of human machine interface and can be more productive (no research close to hand). Who thinks that uploaded humans are not going to be able to figure better interfaces than virtual keyboards?
• Argument maps improve critical thinking, but the interfaces are currently clumsy enough to discourage use (lots of clicking and dragging). Who thinks that being software won't provide a better way to quickly generate argument maps?
• In front of a computer loaded up with my keyboard shortcuts and browser plugins I have easy access to very fast lookup on various web reference sites. At the moment the lookup delay is still long enough that short term memory management (stack overflow after a mere 7±2 pushes) is a problem (when I need a reference I push my current task onto a mental stack; it takes time and attention to pop that task when the reference has been found). Who thinks I couldn't be smarter with a reference interface better than a keyboard?

All of which is just to say that I don't think you've tried very hard to think of safe self-modifications. I'm pretty confident that you could come up with more, and better, and safer than I have.

* Where "pretty safe" means "safe enough to propose to the LW community, but not safe enough to try before submitting for public ridicule"