This  is an interesting position. I think for money, most players won't double this, preferring to hit first if they can. This is quite usual for positions like this, where the back game player gets an early double shot. What usually happens is that if you miss, the opponent is too good to redouble to 8 and plays on for a gammon. That isn't true here. If O misses, X won't even be good enough to redouble, never mind too good! This is because X has 7 checkers buried on the ace point and a startling number of rolls that leave another shot next turn,often as many as 13, all of which leave at least a double shot. Sometimes X has to expose two blots. The icing on the cake for O is that because of this inflexibility, X can be hit, re-enter with 1-5, 1-4, 1-3 or 1-1 (sometimes), expose another checker to a double shot and be gammoned! Of course O is even more likely to be gammoned, but he has first strike capability and should turn it now.
This is probably a redouble/take for money and is very much a redouble (and still a take) in a 9 point match, where X will rarely have an efficient redouble to 8. Both snowie and gnu will tell you this in rollout mode, but the real lesson is seeing why O is unusually strong and X unusually weak. it is those seven dead checkers on the ace, sucking all the life out of X's position! Don't kill checkers is the moral, or you will end up with X's stripped and stacked position, which is utterly inflexible. The 23pt is a particularly good anchor to have in this situation; deep enough to be a nuisance for a long time and surprisingly resilient combined with another higher point, or as will usually happen when O leaves the 21pt, a gap in front of it.
A very common weakness at all levels up to (and including) expert is missing opportunities to recube to 4. The player who is prepared to recube in hugely volatile situations like this is a dangerous beast indeed and will win more matches than the player who tamely hangs on hoping to cash two points. Did don redouble? We should be told!

LOL!

Dorbel's analysis is right on the money including the gnu and snowie analysis in match play.  Money play, hmmm. 

What happened was I doubled, Zorba took, and gammoned me.  As I recall, my chances of gammon were about .16, Z's were .13 or so.  (gnu).  It's a close call, a lot closer than I realized when I actually doubled in this position.

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don