I guess each person finds different exams easier or harder, I for one found the 290 exam to be what I thought fairly easy but infact turned out to be somewhat difficult. I would say that on a scale of 1 - 10 (where 1 is the easiest and 10 the hardest) I would grade the exams as follows.
270 - 1
290 - 10
291 - 8
293 - 4
294 - 4
298 - 5
299 - 8
I didn't need to do an elective because of my existing NT4 MCSE. Of the above exams I only had to resit 290 and 291, the others were passed first time around. Of all of the exams I have sat I found the Security+ the easiest and quickest.
The only thing I can say for the exams is learn more than is required to pass, learn about material that isn't in the exam, I mentioned earlier about RIS not being covered, now whilst it's not covered on the 290 exam it is covered on the 270 (XP) exam and it is something people should know about. The idea of these exams are to show a proficiency in using the product, if you haven't studied it because it's not on the exam then you aren't proficient in my opinion.
Gone are the days of the paper MCSE.