I agree there are some bugs that should take priority over adding new features. The first two you list above are being actively worked on - mainly related to the switch to Entity Framework. The Tax issue is high priority. I do not personally see the png transparency as a major issue however.
Regarding your first post about the rate of nopCommerce releases: The .NET framework continues to advance at an astonishing rate. Part of nopCommerce's popularity is that it is taking advantage of these new improvements in the framework. Moving to the entity framework was an example of this, and although there has been some performance issues, it is still a great move for the project.
Switching to Visual Studio 2010 and .NET 4 allowed us to use many of these features. I work on other open source .NET projects who also did the same. If you are a developer you shouldn't have any problem with this move.
It doesn't matter what changes in nopCommerce, if you are making your own custom changes, you will always have a mismatch. However, by keeping your extensions separate from the core libraries and well documented, this can reduce the pain of upgrading.
Also please keep your language clean in the forums - think of the children :)