I have passed 1Z0-813 - OCPJP8 upgrade exam yesterday with 70%. Studied around a month for this.
This is my lowest score in Java exams so far, but at least I am glad that I passed.
Used the following books:
1. OCPJP8 Exam 1Z0-809 A Comprehensive OCPJP 8 Certification Guide by S G Ganesh, Tushar Sharma, Hari Kiran Kumar G
2. OCPJP Java8 - Part 2 by Jeanne Boyarsky and Scott Selikoff
3. Enthuware mock exams
4. Oracle Study