Several users have reported Safari issues in which the AutoFill function does work properly. The feature functions properly for some time, and then suddenly refuses operate.
Rich DeMuro shows you how RoboForm can remember your info for pain-free filling of forms.
Password auto-filling for Safari on iPhone
Odds and Ends: AutoFill function in iTunes not working properly; Knowledge Base updates
Safari Auto-Fill delays (#4): Deleting form values for speed increase
Safari Auto-Fill delays (#3): Too many form elements; more
Safari: more on AutoFill and delays; memory leaks
Safari: AutoFill can contribute to delays
Troubleshooting Safari: ShareBuilder "working on" problems; Verizon secure site issues; Auto-fill security warning
Tip: Auto-fill substitute for Safari, Chimera