Dunno what to use!

[TatsuJiN]

I used to use one hand but now I switched. To me 2 hands is a lot easier.
(Left Hand)Middle Finger: Left arrow
(Left Hand)Index Finger: Down arrow
(Right Hand)Index Finger: Up arrow
(Right Hand)Middle Finger: Right arrow

[lancer77]

Ahhh...No, I get too confused. One hand is much more natural.

[tnyhwk900]

1 hand advantage - easier to feel the rhythm
2 hand advantage - easier to get complex arrow patterns perfect

Whatever floats your boat. I use 2 hands in this formation:
Left = Left Thumb
Up = Right Index
Down = Right Thumb
Right = Right Middle

Wow, i must be weird.
It's the exact opposite for me. i play Arch0wl style on regular songs, but on stuff like Payon and Minute Waltz, i play one handed, so i can hit the keys faster.
Yep, im weird.

[SiYkO]

I use 2 hands, but the right hand has the middle finger on the up arrow and ring finger on the right arrow. It feels less cluttered, and lets your hands rest more flat. Just rest your index finger on the left fingers, they won't mind.

And i would use 1 handed for everything, except for the up+down arrows together... my middle finger is supposed to watch both, but it cant hit bnoth at same time without completely losing the feel of the keys.

Oh, and if your hands still become cramped, try left hand on L+D arrow keys, and U+R on numpad. It's nice.