Rehdon, I've come here to voice most of the same thoughts that you have. Even though I didn't use the work space manager that much in the overview I still made use of it occasionally. I believe some great things can be done with it if it were to be utilized effectively. Having it just show open windows on the same work space I'm on which I can see are open on the bottom panel doesn't use that space efficiently.
I just saw what you meant regarding the dynamic works space feature and I'm also not a fan. If there's nothing on the work space it should not be visible, but still available. I have a feeling this feature will come (or one that allows us to accomplish something similar) as Cinnamon continues to evolve and we gain more features related to Compiz.
About the hot corner for the overview: If I recall it was bound to the Windows key in Gnome Shell. I would be in favor of the option to disable the hot corner and assign the overview a key binding in future releases. It seems like this would solve the issue of accidentally invoking the overview by moving the mouse too far to the top left. Again, in CCSM something like this would have been possible and I'm looking forward to something like this in the future as Cinnamon develops.
To begin with though, it looks like issue 156 on GitHub would solve your problem of the hot corner being in the same position as the menu.
Regarding the broken themes: The Minty theme is fixed both from the PPA and from DeviantArt. I'm not certain if any of the others are yet. Theming certainly does need a lot of work. It's very confusing that one would need to work with three separate areas to get a consistent look across the system. Cinnamon Settings is certainly on the right track to alleviate this, I think, but everything should be included in there from icons, to mouse cursors, to gtk theme and window borders, as well as Cinnamon themes as it is now. I imagine in future releases of Linux Mint, Cinnamon, rather than Gnome Shell, will be the default so Cinnamon Settings would be able to handle everything since Gnome Tweak Tool won't really need to be included. We're just getting applications that seem to duplicate each other because we're at the bleeding edge and adopted Cinnamon on top of having Gnome Shell.
Overall great job: The menu improvements are definitely visible and appreciated.
*Edit* I went ahead and opened an issue on GitHub for the theming problems, as suggested. That's here: https://github.com/linuxmint/Cinnamon/issues/215