It really depends what you are trying to achieve and exactly what you are interesting in syncing, but your opinion of Kies is almost universally shared. It is one of the most (justly) derided pieces of software I have come across.
Sadly there is no elegant solution like iTunes is on a Mac, where you hardly have to do anything other than click a small number of obvious buttons.
I use SyncMate for calendar and contacts, iSyncr for music and if I just want to copy files to or from the SGS2 I mount the drives as USB on my Mac or Linux computers. There are quite a few other options for syncing such as Salling, Missing Sync, DoubleTwist (music only I think) are the first three that occur to me but there are plenty more.
Desktop integration has been the one big letdown for me moving from an iPhone to Android. On my Mac, perhaps unsurprisingly given an all Apple environment, my iPhone synced reliably and without any effort - it was elegant and utterly simple. It is not possible to achieve this at the moment with an Android phone and a Mac and, as far as I know, the same is true for Windows and Linux users.
