I just got an Asus G73jw A1 with an i-740qm in it. I was wondering the same thing as you. My temps idle at about 38-45c. Even rendering video from video editors, my temps have never gone above 63c.
I monitor the temps with a program called "Core Temp". It's freeware and it puts the temp of each core in the system tray in real time.
Check out this article about i7 temps. Very enlightening.
http
/www.pugetsystems.com/blog/2009/02/26/intel-core-i7-temperatures/
And here
http/www.cpu-world.com/CPUs/Core_i7/Intel-Core%20i7%20Mobile%20I7-740QM%20BY80607005259AA%20%28BX80607I7740QM%29.html
At the bottom of the second link it tells you the max is 100c
But the quick answer is the cooler the better but 50C is nothing. But if I were you I would want to see what it raises to when it's really under some strain.
Try rendering some video, or use the likes of DVDShrink to REALLY compress a dvd and while the system is at work, monitor the CPU usage and temps and see what you get. Be sure the area the computer is sitting on is "normal" and not a cooling pad NOR some insulator like your lap or your bed-spread. Also a wooden desk is still an insulator. A glass or metal desk top is best. Honestly with an Asus and an i7, even under fire, the system should not go above 80c.
Good luck.