Tethering is a really bad idea, as is rooting your phone when still in contract.
The Windows 7 phones are getting better, and soon to eat into the android market.
Why is rooting bad? It is freaking sweet. I rooted my phone. Verizon doesn't check for that nor do they know how. I even jacked my phone up and had to send it in to get a new one. Pretty much the only negative thing is when they sent it back it already had the new OS which made it impossible to root; however I haven't checked in a few months so I should be able to root it now.
FYI, rooting on an Android is a very very simple process and nothing like jailbreaking or whatever they call it on an iphone. It is far less invasive. You are simply unlocking the root directory of the phone for access. Apps still can't gain root access unless you give them permission similar to giving administrative rights to modify some windows folders.
As for eating into the Android market, probably true. Of the big three phone OS's out there, Android is hands down the most complicated while also being the most versatile. There is nothing that Windows or iOS can do that Android can't do with more setup steps. I know my parents have Android phones, but they probably use them to 10% of their capability. A windows phone is probably in their future.
Being a tech guy, Android will always be the superior option to me.
One last thing, why is tethering bad? It is as secure as your home router.
Rooting on Android devices and you will think I am being hypocritical here...that it is fine on devices that are not carrier subscription (3G for example) based, but on devices like tablets that have only wifi.
My Hannspad has a sucky stock rom, but I rooted the device and put a LG990 ROM that supports the Tegra2 hardware in the Tablet. So I can play games and do useful stuff like Netflix, Lovefilm and BB iPlayer. I use my device for study, so it is great that I have access to under clock, thus having a longer battery, etc. I'm finding out that I will have to move to ICS once we have a stable build, and a rooted device is a requirement.
Rooting phones is not a good idea, as some apps out there can take advantage of a rooted device, and cause all kinds of problems. This is well documented. Also you would be breaking the T&Cs of your contract, which could get you into trouble. Like I said about Shmokes wanting to use the tethering, again it is a bad idea. But he is a clever fellow, and I am sure he will refrain from using a dumb WPA2 key. The rest of the population...who knows. I still get calls from people getting their phones hacked. You would be surprised how much trust people invest in their personal devices...
Is your home router secure? Are you sure about that? You just don't have anyone local hacking you....yet.

I keep a password list and change it every month just to be sure, and I also have an Heterogeneous NT4 server box that gives some added protection. Not enough to keep a determined individual out though.
So if you still want to root your phone, well it is your responsibility at the end of the day.