It all comes down to what you are comparing against, compared with my cars that have had standard systems - Civic Type R, Golf Mk4, Smart Roadster, Saab 93, the system is pretty reasonable (though i think i have the 10 speaker system as its an early GTi if it makes any difference) but compared with my full Alpine set up i had in my 'cough cough' Escort (which was blatantly worth more than the car) it isnt too impressive.
I think if you arent an Audiophile and just eant to listen to the radio and cd's in reaonable quality its fine, if you love your music i'd upgrade, the main reason i havent is that i really cant be arsed with having to take the facia off the headunit everytime you get out, and i use my boot space more now,
Cheers,
R