Common problems with this radio include the regulator transistor for the back-light going bad, and the IC-151 RF driver chip going bad. Symptoms of the first problem include the back light flickering, turning on and off at random, running dim, or suddenly changing brightness. These symproms will usually show up a number of months before the back light completely stops working.
The second problem will not give any advanced warning. The radio will just stop producing any measurable power on all bands.
The original 746 (non-pro) seemed to be more susceptible to the backlight problem, while the newer 746PRO seems to have more problems with the RF driver IC chip.
I bought a new 746 about a year after Icom intriduced them, and within 2-3 years, I experienced the backlight problem along with a failure of one of the relays in the automatic antenna tuner.
I set up a web page detailing how to repair the backlight problem at: http://www.ka1mda.org/ham/746/index.htm
Judging by the amount of email I receive, the backlight problem appears to be fairly common.
73, de Tom, KA1MDAwww.ka1mda.org