If you're looking for a literal translation of the TTC then this isn't it - however, it's way more readable than other versions. I think Stephen Mitchell explains himself very well in his Forward:
"With great poetry, the freest translation is sometimes the most faithful. 'We must try its effect as an English Poem,' Dr Johnson said; 'that is the way to judge of the merit of a translation'. I have often been fairly literal - or as literal as one can be with such a subtle, kaleidoscopic book as the Tao Te Ching. But I have also paraphrased, expanded, contracted, interpreted, worked with the text, played with it, until it became embodied in a language that felt genuine to me. If I haven't always translated Lao Tzu's words, my intention has always been to translate his mind."
And I think he does a damn good job. You can compare his translation of verse 15 with the James Legge version below, for example. I know which translation I prefer.
Legge:
"The skilful masters (of the Tao) in old times, with a subtle
and exquisite penetration, comprehended its mysteries, and were deep
(also) so as to elude men's knowledge. As they were thus beyond men's
knowledge, I will make an effort to describe of what sort they
appeared to be.
Shrinking looked they like those who wade through a stream in
winter; irresolute like those who are afraid of all around them; grave
like a guest (in awe of his host); evanescent like ice that is melting
away; unpretentious like wood that has not been fashioned into
anything; vacant like a valley, and dull like muddy water.
Who can (make) the muddy water (clear)? Let it be still, and it
will gradually become clear. Who can secure the condition of rest?
Let movement go on, and the condition of rest will gradually arise.
They who preserve this method of the Tao do not wish to be full (of
themselves). It is through their not being full of themselves that
they can afford to seem worn and not appear new and complete."
Mitchell:
"The ancient Masters were profound and subtle.
Their wisdom was unfathomable.
There is no way to describe it;
all we can describe is their appearance.
They were careful
as someone crossing an iced-over stream.
Alert as a warrior in enemy territory.
Courteous as a guest.
Fluid as melting ice.
Shapable as a block of wood.
Receptive as a valley.
Clear as a glass of water.
Do you have the patience to wait
till your mud settles and the water is clear?
Can you remain unmoving
till the right action arises by itself?
The Master doesn't seek fulfillment.
Not seeking, not expecting,
she is present, and can welcome all things."