excuse me, but i don't see any connection between these two facts.. i mean, I am a noob in N900.. and I have to switch to WhatsApp because really 97% of (jounger) people here in the Netherlands use it, and some people just wouldnt sms.. but these two facts don't have any connection, do they?
@peter i think your instructions should start like this : if you dont have java on your pc go here and install java http://www.java.com/en/download/index.jsp next right click the whatsapp file and open with java proceed with the entering of details on device: enable extras testing repository (if not enabled) and look for icedtea6 (or higher) install place the same whatsapp jar file on the n900 (documents) (then the rest of your instructions)