I'm glad somone spoke up about how my comments seem off. I hope as many ppl read this as possible.
50mg of around 85% is about the right dose for a junkie of about 25 years of almost every day use. ie. after having a shot, you won't feel like another one for a while. I don't back up anything I say with experiences because they all came in a dream to me once, but I hope everyone that reads this takes note.
As for ODing, it is VERY easy to OD. It is not common to die of a meth overdose, but passing out, seizures and real bad experiences are very common.
On a side note, i've dreamt of a junkie bang a half weight of good looking rock and be off their chops loving it, and the same junkie another time having just over half a point and feeling like they might just have had a little too much.
I've also smoked over a point of rock to give minimal effects and another time smoked about a sixth of a point (~15mg) and was well fucked for a good couple of hours)
So like BT mentioned, quality varies, so one must be careful. But if you say you think 100mg of the stuff you get is a nice ride, you are probably getting gear a lot better than others anyways and if you doubled your dose by suddenly getting gear twice as good, you are unlikelly to OD. but might not have the best time in the world
However if you, like many others are used to getting a half gram of smelly yuky stuff of your very knowledgable and freindly DD who says its the best, uncut, base, import, real ice, kuta, sha bu that noone else can get, splitting it with your mate and shooting, you might be in a bit of trouble if you suddenly get stuff 4 times as good.