Hello John, no need to upgrade to intermediate version.
You can directly upgrade to 10.4 version.
Will recommend to move to 10.4 HF2 version which is latest one and does not have any known blocker issues.
As stated by others, there is no need to go for intermediate versions, you can upgrade to any version from any version directly by following the specific upgradation guide available at Home. (docs.informatica.com).
It is suggested to move to latest version 10.4 HF2 in order to refrain any mid version backlogs.
And for your question: are their any known "landmines" in the upgrade process that are not documented?
You need to follow upgrade guide and every necessary steps required is documented in upgrade guide.
Upgrade guide is documented in detailed manner.