We've spotted a number of issues with our controls when upgrading to jQuery 1.4.2. We haven't classified them in details and fixed them on the spot instead, so I can't give you a full list of the issues you might encounter.
If your scenario is easy to test and you can't spot any issues, then go ahead and use it. Otherwise we recommend that you upgrade to Q1. As an alternative you can let the controls use the embedded version and load 1.4.2 separately on the page. This is a supported scenario, but it's not ideal in terms of loading speed.
I hope this helps.
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