My view would be as follows:
The bootrom is a read-only portion of the processor where the device starts up. What we really want to find is an exploit in the new iPad2 A5 bootrom code, just like the ones we have for previous devices, including iPad1 and iPhone4. The thing about a known bootrom exploit is, once we have it, Apple cannot fix it without changing the hardware.
What MuscleNerd is saying is that once the bootrom on the iPad2 has finished its stuff (which is early in the bootup process) it is switched off at a hardware level (powered down) and does not get reactivated at any time until the next time the device boots. This will make it quite a challenge for anyone to actually see what is going in the bootrom by dumping it. Some of the twitter responses are suggesting that a hardware dumping solution would need to be found. i.e. take the iPad2 apart and start soldering! Needless to say that would be a real drag...
Hence, his latest update which states we are likely to see a userland jailbreak first, rather than a bootrom based one...