I'm on O2 and have Data Sense working so it obviously is enabled otherwise it wouldn't work for me!!!
Well, I've noted this on other threads but I've got an unbranded 8X on O2 (UK) and DataSense is NOT enabled following the update to GDR2. I also took the plunge and did a hard-rest twice (the second time without the SIM inserted) and DataSense is NOT enabled.
So, what phone have you got and did it come with GDR2 pre-installed i.e. was it native?