With the update installed, systems with the Intel SSD 600p Series and Intel SSD Pro 6000p Series devices seem to crash repeatedly during startup. The problem appears to be recoverable insofar as you can hold down F8 and roll back the update.
Microsoft is now blocking the update from affected systems until a solution is devised.
The release of the April 2018 update was already delayed after a late-breaking (but unspecified) issue causing blue screens of death was found during testing. Issues with SSD firmwares are not unheard of—some Linux users experienced data corruption with the same drive due to firmware problems last year, and others have had to disable the use of power-management features—and this particular problem is unlikely to be serious in the grand scheme of things.
The solution for Windows 10 may well be similar. Perhaps the latest update is trying to power manage more aggressively (or in a different way) from the previous update, and this is triggering firmware bugs. But this kind of problem does little to instill confidence in the level of testing and validation that Microsoft is doing with Windows 10 in general. These Intel SSDs are not particularly esoteric or unusual hardware, and it seems a little surprising that, among the millions of claimed Windows Insiders, not one of them tried the update and discovered the problem. And if they did, in fact, find this issue, then why didn’t the update get blocked sooner?