( This is long because I just wrote what I thought without really trying to organize it )
So the obvious benefits from all this work: faster startup (at least 21.9% faster) and less RAM usage (about 18.3% less). Most of the hardware support in the stock kernel consisted of modules, and I compiled everything in, but my custom kernel image is only 11.5 KiB larger while reducing the modules folder from 38.9 MiB to 12.5 KiB of just configuration files. (I would've skipped module support entirely if it didn't mean I'd lose my customized boot screen and initrd support.) A less obvious benefit comes from manually configuring the horizontal and vertical screen resolution in the Input Device Support area of the kernel configuration. Because a maximized VirtualBox window is kind of a weird size (1366x672), I can actually specify that weird size and have the mouse work better. Previously, the mouse would jump around the screen if I got too close to the edges of the window. That could just be a coincidence though. If you contact me not too long after this is posted, I could send you my .config file. I would've put it in this entry, but that file is huge. I may try this with a non-virtual machine in the future. After all, I still have the kernel source on a server on my local network.