Update and final thoughts:
Installation went smoothly as well on the W7-32 bit bloated internet desktop. This PC has a separate PCIe usb controller. The same project I mentioned above, is not able to run efficiently. Not surprising though, as this PC is not setup to record. Antivirus, Skype, Aero, all of the no no's for recording are on it. Not to mention it is only a dual core AMD processor. Loaded a 20 track project, and all was fine.
I am not sure there is any need for me to test the drivers on XP or Vista. I have never heard a problem with those. Figure if W7 works, then the drivers are likely solid for the others.
Regarding issues that I had heard involving USB disconnection. I shut down and restarted the i7 10 times. Each time the 800 connected correctly. Though, the 800 must be powered up 'after' Windows is loaded. If USB cable is disconnected while a program is opened, you must restart the 800 to regain connection (simple off/on). A possible PITA, maybe if you are lazy. Just shut down the unit when not in use. Put it on a power strip with your monitor amp. Just a procedure thing. With the Release Driver box checked in Cubase, input back and forth between Media Player and Cubase was seamless. I left a Cubase project open overnight (9 hours). This morning, connection was still solid.
The preamps seem to have just as much gain as the 1641. And as clean. I will wager that they are the same as the 1641/1800 ones. I actually seemed to have slightly higher input level into Cubase with the 800, and input gain at max on both units. I tested with an SM7b, and it was just getting to the edge where sweetness begins. 1/4" cables inserted into the multi jack on the unit 'do not' bypass the preamp. Or at least the level is variable with the knobs on the face. That being said, the SM7b connected through my X73i, sounded the same to my ears, as line in on the 1641, with the level of the preamp/input level on the 800 turned all the way down. The HiZ guitar inputs sounded good with bass guitar plugged in directly.
My findings, at least on my systems, is that the unit is absolutely solid with a properly installed driver, and optimization of PC, as well as proper delegation of USB controllers. I however am disappointed that I couldn't get the unit to work with USB3.0 port. There is mention in the literature, about using only the actual USB port that the driver was setup with. Funny enough tho, I installed the driver with the 800 in the USB3 port. It made some pops when opening Cubase, but did not produce audio. But when I moved the USB cable to a front USB2 port, it worked fine. Go figure.
Hope this helps anyone with questions about the Tascam US800.
Jimmy 'HR's unofficial Tascam interface dood'.