Is there any benefit to optimizing my network connections (TCP) using tools like the TCP Optimizer?
If there is a benefit, how does one do it right?
It depends. Depending on the type of network you are on and the applications that you typically access, tweaking Windows standards may or may not help.
If you're using frame-relay WAN links, tuning the TCP Window Size has a fairly dramatic impact on circuit utilization. Depending on your ISP/WAN connectivity, adjusting MTU or other parameters can improve overall performance as well. On the flip side, if you're primarily accessing hosts on a gigabit or fast network, you'll want to adjust your settings upward to optimize throughput.
There isn't a single answer. If you're looking to optimize DSL or Cable connections, I'd suggest the broadband reports forum for tips. Otherwise, in an enterprise environment its all about understanding how your users work and how your networks are implemented.
duffbeer pretty much said it all but just keep in mind that when you start fiddling with such settings you have an equal chance of screwing things up. The Windows defaults, and I would assume the defaults of other operating systems, will generally be very good, if not the best, for communicating with other devices.