I decided to install CyanogenMod 7 on my HTC Inspire 4G and use it in place of the stock HTC Sense ROM. I miss the Sense interface a little but the advantages of running a ROM based on the AOSP outweigh the loss of HTC's eye candy and stock apps. The process I learned from the xda forums on making a goldcard and then using the Simple One-Click Root and S-OFF tool in Windows to get the Inspire in a state where CyanogenMod can be installed was fairly simple. You can also follow the CyanogenMod wiki if you want to do this via the command line in Linux.
Rooting processes get simper over time as new methods and tools get developed so if you're reading this far off in the future you should head on over to xda and see what's new in the Inspire forums. Maybe some other tools have been developed. You should also read each thread fully, or if it's too much text at least skim through it. The process will WIPE YOUR PHONE so make backups of everything first. You'll also need to temporarily disable your antivirus software if you're using the Windows tools as they will likely detect the rooting tools as being Unix exploits and mess with them. Here are the threads I followed when I rooted my Inspire:
First you'll need to make a goldcard out of the microSD card that came with your Inspire. It's a simple process, really. You can do this without removing your SD card from the phone by switching your phone to disk mount mode when appropriate in the process.
Once you've used the GoldCard Maker tool, you can use the Inspire Simple One Click tool (which actually requires several clicks) to install a rooted stock ROM. This is the part that will wipe your whole phone, so make sure you're backed up.
If something goes wrong at some point you can flash back to stock by following the second post in this thread: Return to Stock
If everything went as it should have you should have a rooted stock ROM installed. Now you can keep that or install a ROM that has the features you want. There are several Sense-based ROMs out but I wanted CyanogenMod 7 for various reasons and installed that using the Rom Manager app. After I installed CyanogenMod 7 RC2 I flashed this kernel to get a small overclock with SetCPU and the battery fix, as the RC doesn't have it. I flashed before RC3 had been released, that has a battery fix built in so you don't need the custom kernel.
Following the threads on xda and using the easy Windows tools make rooting the Inspire fairly fast and easy, it only took me a little over a half hour. I spent far more time reading the threads and working up the courage to try than I did actually doing the deed. Normally I'd do this sort of thing in Linux but since I had booted Windows anyways to play Dragon Age 2, I figured I'd save a little typing by using the gui tools the devs at xda had cooked up.