IMHO, I do not think GPS is a must have, but it depends on each user and yours necessity, and not a must have feature. If you always go/travel to unknow places, it should be a must have. Otherwise, if you stay all most time in your own city/state, it is just a luxury. I have a HoluxSlim 240 and I think I do not real use/need it 6 times in the year.
For me, the major deciding factor are:
1. Size;
2. Weight;
3. Autonomy;
4. Wireless.
