There's too much here to respond to this late at night, but to get fine control over brightness, just touch and hold the battery icon, there's a link to screen brightness, and you get a slider.
Your other complaints seem very subjective, though no less valid, I don't know...but I use my SP3 for real work and play every day and it's working great.
Yea I am aware that you can do that. But that is soo annoying. The charm bar idea is what Windows 8 was differentiated itself from Android and iOS, where you can slide a panel for quick access to brightness control, wireless, and other options. While Windows 10 keeps that idea, instead of having a slider pop-ing up for the brightness, you have this button. And if you want finner control, you need to go in settings. This is very annoying.
Might as well be like in Windows XP, where you need to go dig through Control Panel to find the mobility center, and control the brightness.
My complaints aren't subjective. They are facts. I never said that I am not going to upgrade to Windows 10, I'll upgrade day 1 to it, I can assure you that, on both my systems. The upsides are far more than the listed downsides. And I know that most of my downsides listed can be fixed with updates form the app store and Windows itself. They are not critical issues. But they are issues that i think we should not ignore.
There is no denying that Windows 10 is being rushed out. Many features of Windows are by Microsoft: "Coming after Windows 10 is out". So it will either be a App Store update or maybe under Windows 10.1, which will probably be released next year. This is unlike Microsoft to do this. And I think it shows that Windows 10 is being rushed out. Another fact of this, is that many manufactures made computers won't have Windows 10 on them when you buy them in the store on July 29 and a few days after, as manufacture barely got enough time to prepare systems with Windows 10, and replace them on store shelf. My guess is that they are focusing on the popular models, and the rest will be upgraded within 1-2 weeks after Windows 10 is released.