New doc info from @mrocklin

doc/tutorial/using_gpu.txt

@@ -610,16 +610,11 @@ Modify and execute to support *stride* (i.e. so as not constrain the input to be
 GPU Async capabilities
 ----------------------
 
-Since Theano 0.6, we started to use the asynchone capability of
-GPU. This allow to be faster, but some errors are raised later, at the
-wrong place. This mess with the profiling of Theano apply node.
-In both case, you can use the NVIDIA driver feature that when
-environment variable CUDA_LAUNCH_BLOCKING=1 is set, all kernal call
-get automatically syncronized. This will restore to the old beavior
-that provide good profiling and error message.
-
-This feature interact with Theano garbage collector of intermediate
-results. To get the most of this feature, you need to disable the gc
-as it insert synchronization point in the graph. Set the Theano flag
-allow_gc=False to get event faster speed! This will raise the memory
-usage.
+Ever since Theano 0.6 we started to use the asynchronous capability of
+GPUs. This allows us to be faster but with the possibility that some
+errors may be raised later than when they should occur. This can cause
+difficulties when profiling Theano apply nodes. There is a NVIDIA
+driver feature to help with these issues. If you set the environment
+variable CUDA_LAUNCH_BLOCKING=1 then all kernel calls will be
+automatically synchronized. This reduces performance but provides good
+profiling and appropriately placed error messages.