Upgrade from 4.01 to most recent version?

I just got a MPC and i'm told it came with the JJOS

It only has version 4.01 and i see here you guys may be up to 4.6+

Any reasons why I should or shouldnt upgrade?

in short: absolutely no reasons.

before hand you might wnat to read the bug fix pages on JJ's website.

Yes, a lot of useful as well as nice features have been added since 4.01.