Great info in the compendia, yes, and the tests are actually...tests!.
The online seminars are a slacker way to get ceu's--the tests are gimmes. If you want less challenge and less contact with other humans, that's the place to be. There are less infomercials than there used to be, tho.
TC, if you still haven't joined ISA so you can take the Arborist News CEU's (which are a good way to go), there are many other worthwhile ways to get em:
I got enough for all 4 certs in a few months, but keep getting em cuz--the goal is not to hit the magic number and slack off, but rather the goal is to keep learning!