C182 pilot on IFR flight plan in VMC experienced attitude indicator failure and elected to continue to destination. Weather at destination was worse than forecast requiring a partial panel VOR/GPS approach with significant altitude and heading deviations to get below the ceiling at 800 FT AGL.

Narrative

My attitude indicator failed in-flight; in IMC; approximately 70 miles SW of my destination. Weather was reported in the area as 2900 BKN and 4000 OVC with 7 MI visibility which should have allowed for a visual approach. After determining weather from 2 stations which confirmed each other; I elected to continue since it should have been a brief descent through IMC which did not strike me as unsafe with partial panel situation; provided the approach was to be conducted in VMC. However; weather conditions deteriorated significantly in the next 30 minutes and I was still IMC 3 MI from the airport at the lowest altitude that approach could give me; 2300 MSL. Rain and light turbulence were making partial panel IFR challenging and my headings and altitude were deviating. I notified ATC of the malfunctioning AI; but elected not to declare an emergency. I requested vectors for the VOR/GPS approach to try and get a controlled descent to VMC; since this seemed a faster route to visual conditions than returning to the south with indeterminate weather. The approach was successfully executed and I broke out at 1300 MSL (800 AGL) and was able to land. However; again due to partial panel indications compounded by light to moderate turbulence; my headings and altitude were deviating from ATC clearance; heading up to 25 degrees and altitude up to 200 FT. The chain of instrument failure; unexpectedly low ceilings and my own lack of very recent partial panel experience all led to imprecise IFR flight and likely reduced safety margins. To prevent a recurrence; additional focus on partial-panel proficiency and a more conservative view of weather in the event of a near-emergency to keep the situation from deteriorating would have been advisable; and at the initial indication of AI failure; I should probably have requested vectors to the nearest airport reporting VMC.