i would get the refurbished unit. yes id upgrade.
Is it worth upgrading to a new macbook pro from a 15 inch 2.4 unibody macbook pro? I would look at a range of macbook pros
1) 13 inch macbook pro
2) 15 inch macbook pro $1699
3) 15 inch macbook pro $2000 with graphics card
Options 1 and 2 would be a performance downgrade for you in the graphics department. You'd also lose your expresscard.
There's really no compelling reason to upgrade at this point.
that's a question you need to answer yourself.
do you ever find your current battery running out?
do you do serious graphics work?
remember, in 6 months there will be another MBP out with an even better battery and faster specs (core i7?), and you'll be asking this same question.
is it worth looking at the high end 15 inch macbook pro $2300, with the better graphics card? i am not a gamer but would like to future proof.