UploadWizard brings to Commons make it a no-brainer for you not to use it. It is awesome and, with the improvements that went into production this Wednesday, the moment where it will be a no-brainer for the WMF not to replace the current Upload functionality is near.
The current iteration of the UploadWizard does create a thumbnail when using Ubuntu, the statistics functionality is enriched and many more localisations found their way in the software.
Over 10,000 uploads have been done with the UploadWizard, important feedback has been provided to the developers and one of the major worries left is that the localisation for many languages like Spanish, Japanese and Chinese is still lacking.
You can find the current state of the localisation for your language here and, you can start localising for your language here. You can make two MediaWiki developers, kaldari and neilk_ really happy when you complete the localisation for your language, they really really have done what they can to provide you with the best usability. Now they need you for that missing link that is outside of their competence; supporting their software in your language.