The HTC Inspire 4G is the first Android phone I've ever owned, and this is my first phone I've ever rooted and have installed a custom ROM on it.
I followed this video:
YouTube - Unleashing the HTC Inspire 4G [Root, Unlock, S-OFF] to root my phone with absolutely no problem.
When rooting, make sure you type MMC0 when using the adb shell /sys/.... command on the CMD window! Don't do the same mistake I did by using MMC2!
You can also follow this video:
YouTube to install a custom ROM on your phone!
Happy Rooting!
PS - I would also like to add that after rooting and installing a custom ROM, I'm getting the follow upload and download speeds:
http://www.speedtest.net/android/33878328.png