Hi,
Other things you may check are:
1. Harmonics
2. Frequency (its not always 50Hz!)
3. Noise (The A/C waveform may not be perfectly sinusoidal... again the sine-wave itself may be riddled with kinks in the "S" waveform)
While earthing and voltage are pretty easily checked by your local electrician, for Harmonics and Frequency you need specialised equipment.
BTW I'm not an elec engineer. I came to know reg above from the elec consultants I coordinate with, in construction industry.