You aren't speaking to Apple here. This is an Apple moderated forum for discussing features, and troubleshooting. Apple menu -> System Preferences -> software update has options to disable automatic downloads, although the Mac App Store update itself for Snow Leopard does enable automatic notifications of updates. While a nuissance, you just have to say later, and choose only to update once you have read the documentation to verify it will work with what you have. Always backup your data before allowing any updates.
For direct feedback to Apple, which may only impact future operating systems, http://www.apple.com/feedback
If you find a specific update has compatibility issues, you are welcome to sign for a free online developer account at http://developer.apple.com and submit a bug report at http://bugreporter.apple.com where you can know at least if it is something reported before. But you won't get to divulge that information here because of a nondisclosure agreement,