Updosing seems to be a bit of an Australian thing- to get fuller-bodied, chocolatey shots I believe.
Ive had a bit of fun experimenting with different doses and its amazing the different flavours you can get when you up-dose, down-dose etc.
Yes, you can get a great shot with a lower dose. (I suspect it might take a little more work to get a great shot with a lower dose, as updosing may be a bit more forgiving - I might be wrong though).
Really, its all about what your tastebuds like! If they prefer an updosed shot, then updose! If youd rather a normal dose, or a lower dose, then do that! Try a bean or blend both ways and see what you like better! I usually am a bit of an updoser, but theres a particular Kenyan that I loooove down-dosing as it brings out this lovely jasmine-like, coffee-blossom aroma and it tastes like green tea. Amazing.