Nope, not necessary but may improve signal/wi-fi performance - there are reports from other users of this. If you're having issues an update might be worth a try, and you can always reflash the original if you're not happy. It's hard to be subjective as I haven't done any scientific tests myself yet, and I had no problems with the previous versions. However I'd say that the signal strength meter is showing on average an extra bar with the latest radio installed here.
Just be aware that it's not as seamless a process as the ROM update; you get prompted to reboot after the initial unpacking and installation, but the phone then boots into the recovery image a second time and does the 'formatting cache...' thing. You get no reboot prompt this time, and it may appear that the process has hung. Just reboot from the menu anyway and it will restart normally.
Edit: Oops, too late. Glad it worked anyway Phil.
@3rd-Geer: No need to wipe. Copy, reboot, run, reboot.... sorted! Differences? None here that I've noticed performance-wise. A bit of internal memory will be lost due to /dalvik-cache being relocated back from the /system/sd for performance reasons but I find v2.0 just as snappy as v1.5.
/Al