These days the probe is normal in the absence of other positional factors. For example, consider the following diagram. Here the approach in the upper right is the first event of the game so there is nothing else of real significance on the board. Black approaches at
in order to get White to commit to a reply. If White replies with 
, Black will 
and extend to 
. In this case White would rather that were at "a", which would better support an invasion at "b". However, if White goes ahead and plays "a" instead of , Black will switch to "c" and only extend to "d" rather than .Your game situation is different however because of the other stones on the board. The advice is actually incorrect. In this case it is naive to expect Black to continue with
at "a". That is too low and fails to make use of the marked stones. In fact Black will peep with and, if White connects, then continue with 
or "b". So in fact the pros do not play the probe in this position. Instead they connect immediately at 9 with 
. Two more points from GoGoD:
* In the position below pros are twice as likely to approach with "a" rather than
.* In the seventy examples where White does approach high at
, Black responded at 
six times more often than at "b" and responded four times more often at "c" than "b" in order to capitalize on the presence of the marked stones. As always YMMV! 
And the bit about the peep makes sense, I thought about it during the game, but it was never played out. I'll try and pay more attention to those approaches.
immediately. To do so is going against the flow of the game: with white's probing approach he is asking black how to answer, in order to decide how to handle the top. If black doesn't answer white must press the advantage with a double approach (low looks best, I remember at the EGC this year in a similar sort of position Ko Juyeon 8p said "double approach never bad"). Maybe later white will save the stone that approached 3-4, or black will kill it whilst white gets big moves elsewhere. To save the stone in gote is like making a ko threat, your opponent ignores and resolves ko, and then instead of following up on your ko threat you answer the ko!
ends up slightly misplaced: white has successfully turned it into a slightly bad move. The thinking behind the pincer is that you are turning it into a good move as forms a good shape connecting the 4-4 stone to the pincer on hoshi. In the fighting that develops, white may well come to regret playing the approach at 
as a hane at 
, although it is sente and makes white have a little more eyespace, it also makes black's corner totally alive. In the position below white will probably play the a-b-c-d exchange soon as this makes e sente, which strengthens those stones considerably.
the diagram below. This anticipates that white will make influence and preemptively erases it. This strategy is possible in this opening because black has played tightly on both sides (look at the marked stones).
. Note that 4 at 'a' looks like a good move, but it's not. White just plays the counter at 'b' and suddenly it's very hard for black to maintain connection along the top. That's because the 'a', 'b' exchange gives black shortage of liberties. Note that white now wishes that he could approach from the other side in the lower right. That exchange has turned into a bad move for white.