For those who haven't rooted (thus MSL Reader isn't an option), you can easily use CDMA-Workshop. The main trick is getting the proper software installed (HTC Sync, drivers, etc) and then using it in various ways, depending upon your situation and operating system. I'm running Windows Vista x64.
First, you have to know what COM port the phone is on, when connected via USB. When you run CDMA-Workshop, there's a choice of 25 ports, so it would be major pain testing connectivity on all of them. Normally QPST can help you in this regard. It should show your active phone on one of the listed ports when you run QPST Configuration. However, it won't always see the phone as-is. Sometimes you have to put your phone into diagnostic mode, via ##3424#.
I'd had a slightly older version of QPST, so I uninstalled it and put the newer one on (b323). After that, QPST would not see my phone on the available ports. However, what I noticed when I plugged my phone in, was the "new device installed" dialog pop-up. If you click on it, it'll tell you what port the phone was installed on. In QPST, you can select to add additional ports. It'll show you a few in the list. If the port that the phone is on isn't listed, you can select one of the ports and modify it to match. In my case, it was port10. Upon adding it, QPST showed the phone active in the list.
CDMA-Workshop requires you to select the active port that the phone is on and then connect, in the Main tab. Make sure QPST is stopped, or else CDMA-Workshop will fail (only one program can access the port at any given time). Once connected, perform a read for the basic info. Then go to the security tab and perform a read with the default dropdownlist selection. If it fails, try restarting your phone. In my case, it didn't work the first time. Restarting the phone worked, but I also had to put it into diagnostic mode. Once that was done, I connected, performed a basic read, then did an SPC read from the security tab. I got the MSL ID with no problem.