More IFR with VFR GPS questions

Hi Folks-

Without descending into the madness of the other thread, I have a
couple of questions regarding the use of a VFR GPS while IFR.

Hypothetically, let's say I was flying IFR from Santa Monica, CA to San
Jose, CA (SMO to RHV). The weather is CAVU. I am filed /A and cleared
via a fairly standard route on victor airways. Just past the mountains
and still 150 miles from RHV, Oakland Center asks me if I am "GPS
equipped." I answer in the affirmative as I have my trusty Garmin 296
mounted on the yoke. I am then cleared direct GILRO, direct RHV and I
accept the clearance. I proceed to fly said clearance and land at my
destination without futher issue.

I realize this is common practice. It seems to me it would not be
strictly "legal" as I would be relying on the 296 for primary
navigation.

My questions:
--Where did this situation actually break down in terms of regulations?
When I affirmed I was GPS equipped (knowing that mine is not
certified)? When I accepted the new clearance? Never?
--In CAVU weather, the risk of this becoming a problem is basically
nil. However, in IMC, I would consider it to be potentially
problematic (i.e. the 296 goes Tango Uniform and I'm not exactly sure
of my position using my trusty VOR's). Would you consider this risk
neglible? Would you accept or not accept this clearance depending on
the weather? And why?

Thanks for your thoughts.

Cheers,
--Chris