I haven't really used tethering except to see that it works. Today I noticed that webpages redirect to a T Mobile page offering their tethering service. This is on the $30 plan with 5GB data
edit: but the fix seems as easy as a user agent switcher extension
edit2: because most user agents that work make a mobile page display, I looked for a UA string that works while providing the desktop site. Someone mentioned Linux Mint working with hotspot and this is the first one I found on google. It works!
Mozilla/5.0 (X11; U; Linux i686; en-US; rv:126.96.36.199) Gecko/2009042113 Linux Mint/6 (Felicia) Firefox/3.0.9