I am using qTranslate at the moment and contemplating to switch to multisite later.
The advantages of qTranslate:
– you can easily share data between languages, you save space
– quicker site update in more languages at the same time
The disadvantages of qTranslate:
– questionable support in the future
– some functions are still missing
I think WordPress should offer a good multilanguage solution out of the box. Multisite is good, but it’s more space-consuming and takes more time to update the different language versions totally separately.