I had the free vouchers from IBM but could never gather enough courage to actually sit for the real thing till the last moment.
Here is the sequence of my exams
IBM 285 (March 25th 2004):- This is an easy one but does expect you to know a lot about the perspectives/menu etc. You need hand on experience with WSAD.
------ Break ------ was away to my home country from April 2nd to April 25th ----------
IBM 286 (May 24th 2004) :- It is tougher then the 286. Expect you to know about Java and Web perspectives. Also you would better off if you have been doing web development or studying for scwcd.
IBM 287 (June 12th 2004) :- This one is I guess the toughest out of the lot. You should still be able to pass this one if you don't have much hands on experience with WSAD. I used Kushner's guide for 287. The exam is highly focused on EJB's..so I believe if you go through the relevent chapters on Howard Kushner book and read a good book on EJB you should be all set. Don't miss http://www.ejbcertificate.com . Unfortunately, I saw it after I had taken the exam. You can find the relevant parts on ejbcertificate.com from the 287 test objectives here http://www-1.ibm.com/certify/tests/obj287.shtml It is an amazing tool and the best part..it's FREE.
IBM 340 (June 28th 2004):- Well can't say much about this one as it is totally product specific. The exam is not tough and one should be able to clear it if you have played around enough with Websphere 5 admin and know the parts and architecture well enough. The pass is just 55% ... and the exam is quite close to the Sample test.
IBM 486 (June 30th 2004):- This is the last one of the lot and definately the one I enjoyed the most. I was also most scared of this one. The exam did not turn out to be that tough.... I used Whizlabs for this one... it makes you get used to reading long questions and gives you a good explanations on why certain answers are wrong.