Personally I like transparency as long as it doesn't affect readability or get in the way. I most certainly don't like plain opaque colors without any gradients - it's like the professional designers don't want to make any effort at all, even a kid can draw up colored rectangles in Paint. Aero Glass in Windows 7 was not plain transparency - it had blur and glow. So the glass areas of the shell such as Taskbar and Start Menu weren't completely unreadable if something appeared behind them.
Windows 8 removes these DWM effects. In Windows 8/8.1, the taskbar is too transparent. But it is always on top of most programs (except full-screen ones). The same is not true for the Start Menu. Anything can be behind the glass area of the Start Menu so it can't simply copy the taskbar's level of transluency. If you make the Start Menu the same, it becomes unreadable. Like this:
Start Menu replacements have a challenge on their hands. People expect the Start Menu to match the Taskbar color so its feels "native". There are 3 options: either make the taskbar fully opaque and the Start Menu opaque too (ugly but readable), reduce the Start Menu transluency (remains a mismatch from taskbar shade), or use unsupported methods to reduce transparency of both the taskbar as well as the Start Menu.
For Classic Shell, the default skin that ships with it on Windows 8 is far less transparent than the taskbar so it looks like a complete mismatch (ugly) but is readable. There is a separate downloadable skin that tries to be as transparent as possible without affecting readability too much (still doesn't exactly match the 8.1 taskbar but comes close, it doesn't stick out like a complete mismatch): http://winaero.com/b...aero-skin-2-0/.