Hi!
I own Asus G750JZ and I have just now upgraded it with Samsung Evo 840 250GB SDD. While I was installing games via Steam and doing some other things I saw that the T was around 47°C.
25 C - 35 C is ideal, though more difficult to maintain in a laptop than a tower. 35 C - 49 C is acceptable, while 50 C is on the very tip of being acceptable. Over 50 C is associated with higher failure rates.
If the drive gets to 50 C, start looking into ways to improve the cooling!