all depends on what your looking for, if your number chasing i'd do other mods first; if your just looking to improve the responsiveness of the car then get it done.
but if pennies are a bit tight this month i wouldn't rush into it. especially if you're going to drive it through the winter. i'd get through that first then see what the banks like after Christmas.
it will definitely have a positive effect on the car, but its never going to turn it in to a snarling beast. FI is the only thing to do that.