From reading the wikipedia article, CLEP tests are multiple-choice exams, so I guess they can't be that difficult. Also, you should be able to gauge how difficult the tests will be by taking the Official Study Guide practice test, which is approximately the same difficulty as the actual exam.
Yes I did. It was basically a reading comprehension test.
The computer will read a story of a couple of minutes long like: Maria and Juan went to the supermarket to buy some apples and oranges. They met their neighbor Pedro who was buying chocolates.
Then the computer will ask you 1-4 questions per story. The computer will only read the story once.
I think they have some grammar stuff, you have to select the right tense etc.
You have about 1 1/2 to 2 hours to finish the test.