Writing negative reviews does not help! If anything it makes it more difficult for developers to get downloads, which will lead to them caring less and having less incentive to update their apps. Remember that Windows 8 is a relatively small app platform, and most developers are not making money, so have no incentive to update low-rated apps that make no money.
It can't be stressed enough that you need to contact the developer directly (email for example) if there is an issue with their app. The developer won't see your reviews 99% of the time.
Most developers want their apps to work, and will happily look into a request to fix something. I personally respond to every email I get from users regarding any bugs or issues, and I always patch my apps ASAP - usually the same day I find out about the issue. But I have no way of responding to negative reviews, and no easy way to view those reviews from all the different markets around the world. If I have to prioritise (and being a 1-man team I have no choice), then I will focus on the apps with the most downloads (and thus usually the highest ratings) first.
Remember the dev may not be aware of the issue. Some issues only occur in specific situations. I have a user of one of my apps who is frustrated that it doesn't work, but I can't replicate the error he gets on several different setups, and no other users have reported the same issue. Don't sit on an issue for weeks expecting an update any day now - the developer may not even know about it.
Unless a developer has done something weird/wrong in their app it should work flawlessly on Windows 8.1 (without the added functionality such as different screen layouts of course).
I've personally not experienced any issues with 8.0 apps running on 8.1.
Bear in mind it's not trivial to update apps to support 8.1. The developer will either have to abandon the 8.0 version or have two separate versions, meaning double the maintenance in many ways. Many apps are developed by hobbyists and individuals who don't have the time (or incentive) to spend time updating their apps.
Microsoft should have done more to ensure compatibility. It's annoying that you can't support both screen layout models in a single app version. In my current projects I have decided to go 8.1-only because I can't maintain 2 copies of everything. But Microsoft has done a poor job of getting people to upgrade to 8.1.
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