They are GOOD. It isn't a full sim, which is expected since it isn't trying to be one, but it is night and day better compared to wii sports golf. Timing and getting the remote back to "square" at impact are crucial, but having good overall swing mechanics helps a lot. Out of my 3 buddies who have tried it so far, 2 of them who play golf did really well, and the other one who has never played couldn't get a straight shot to save his life.
The "ideal" swing is pretty darn close to a good swing on the course or range... you can eliminate any sort of wrist action (making it more of a arm-only swing compared to real golf), but everything else is pretty realistic about the physics.
I have played all of the hot shots games since #1, all of the tiger woods games since 2001, and a bunch of the smaller titles like swingers, mario golf, etc. This game beats them all on fun factor, and if they were to fix a few of the minor bugs in a sequel, this game would rule as the overall best by far.