Depends upon what you call important. But with all of the hubbub going around about the Spectre and Meltdown flaws, you can bet that the updates right bout now are pretty important.
Of course, Pixels (usually) get the updates the fastest - they run stock Android, which Google patches and releases very early every month. Almost every other manufacturer takes those updates supplied by Google and adds in their own stuff - overlays, assistants, device specific apps, etc. - so you have to wait longer for them.
The only exceptions AFAIK are devices that also run stock Android (which, I think are Android One and a few others and that's it).