hm..check for the warranty, thats the most important one..should say it from samsung electronics warranty, not from the shop..
then i think, check the battery and the back of ur phone..ensure theres written FMG or Brightstar..
and also confirm that you will be given all the typical samsung accessories for ur JET..
after you got it..check for:
1) GPS: some user couldnt get it working..so check ur gps signal thru google maps or by the geo-tagging feature(camera)..
*resetting ur phone should fix it if ur gps not working
2) Install NPS on ur pc, try connecting ur phone..some users also couldnt get the NPS functioning with their phone..its important actually to get ur NPS working with your phone so u can backup all your contacts, task, etc. Alternatively, transferring audio, video files can be done with the mass storage option..
*install the latest NPS software should fix the problem..sometimes the software cd is not the latest one..
3) Organize ur settings, probably the priority is to configure your network, security and phone settings
Java programs, recommend to install SNAPTU & MORANGE(both social networking apps.) and works perfectly with JET..
If you use english as your phone language, u can flash ur phone to S8000XEIG1 or S8000XEIG2..Most noticeable improvements on touch sensitivity, browser, sms/qwerty layout, widget download bug fix and additional navigation software..