I just got my 60gb z3 upgrade today for my z1.. holy cow got it in 2 days.. Absolute drop in hardrive, havent yet to play with the navi yet but everything looks good and working great.
But yeah just the 4 weak screws that were tightly fastened, i have a good philips screwdriver that is tight and snug and it still strips, only 2 stripped though, the other 2 wasnt that tight... I ended up drilling the 2 stripped screw and it came out fine without damaging the original HD threads.
I would highly recommend this one beyond anything else, but I would say the 4 extra screws are must and well