What does Lady Macbeth say about her husband's character and do you agree with her estimation of him in Act I scene 5 of Macbeth?

Lady Macbeth says that her husband is soft
and she worries that he cannot do what is necessary to become
king.

When Lady Macbeth gets the
letter from her husband describing his interaction with the witches, she is thrilled
with the predications that he is going to get a promotion and then be king.  However,
she does not believe that he has what it takes to make it
happen.

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Glamis thou art, and Cawdor; and shalt
be
What thou art promised: yet do I fear thy
nature;
It is too full o' the milk of human
kindness
To catch the nearest way: thou wouldst be
great;
Art not without ambition, but without
The
illness should attend it … (Act 1, Scene
5)

Basically, Lady Macbeth
thinks that her husband is weak, and that if there is violence to be done, he will not
have the guts to do it. When she says that he is too full of “the milk of human
kindness,” she is saying that he is too gentle to do what needs to be done.  He is too
nice a person.  She implies that he needs her to “chastise” him “with the
valour of [her] tongue” and guide him.

Is this the Macbeth
we know?  Lady Macbeth paints the portrait of a gentle man, but we have been told that
Macbeth is a valiant and ruthless soldier.  The bloody sergeant describes Macbeth’s
deeds in battle, and tells of how he defeated the Thane of Cawdor valiantly with no
thought of himself.

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For brave Macbeth--well he deserves
that name--
Disdaining fortune, with his brandish'd
steel,
Which smoked with bloody execution,
Like
valour's minion carved out his passage
Till he faced the
slave;
Which ne'er shook hands, nor bade farewell to
him,
Till he unseam'd him from the nave to the
chaps,
And fix'd his head upon our battlements. (Act 1, Scene
2)

In this description,
Macbeth cuts a bloody passage through the battle, killing everyone in his path, and then
slices the guy in half.  It certainly seems like he had no problem either with violence,
knowing what to do, or doing what had to be done.  Lady Macbeth was nowhere to be found
on that battlefield, and Macbeth was brave enough.

Why
then, does Lady Macbeth describe her husband as weak?  Could it be that he is just
principled?  He knows that killing Duncan is wrong.  Even as she tries to talk him into
it, Macbeth will suffer a crisis of conscience because of the fact that Duncan does not
deserve to die and Macbeth does not deserve the crown.  To be king would never have
occurred to him until the witches put the thought in his head.  Then, of course, he
demonstrates sound ambition.  His wife does not believe he is ambitious?  She should
have heard his soliloquy when he learned that Malcolm was chosen as heir to the crown
instead of him.

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The Prince of Cumberland! that is a
step
On which I must fall down, or else
o'erleap,
For in my way it lies. Stars, hide your
fires;
Let not light see my black and deep desires … (Act 1, Scene
4)

Clearly, based on this
outburst, Macbeth is ambitious and moody.  He certainly seems to believe at this moment
that he deserves to be king, and he is very upset when the honor is not granted to him. 
Malcolm is the natural heir to the throne, but Macbeth does not see it that way. He
wants what he sees coming to him.  The witches painted a future of glory, and now that
is all he can think about.  However, later, when he is back in his own castle with a
cooler head, he has second thoughts.

It often does seem as
if we have two Macbeths.  There is the valiant and ambitious Macbeth who can plow his
way through a battlefield and order the murder of his friends in cold blood, and there
is the brooding and cowering Macbeth who takes orders from his wife and finds himself
wracked with uncertainty and guilt.  Macbeth is manipulated throughout the play at
almost every turn—by either the witches or his wife.  It is no wonder that he shows
signs of instability.