“Take long/longer/less long”

They seem grammatically correct but the first and third are awkward. Better:

• This took a long while. (or "time")
• already fine
• If we do Y, it won't take as long.

It's tricky because none of these are really *wrong. They range from ✓good to ?questionable.

I would say the basic verbose form is take a long time. To my ear it only sounds good to omit a ... time when using a comparative or superlative form of long, or a negative. I don't think any other phrase behaves this way.

Absolute:
✓ It took a long time. (29.3 million Google hits)
? It took long. (3.5 million)

Negative:
✓ It did not take a long time. (1.5 million)
✓ It did not take long. (10.8 million)

Comparative:
✓ If X, it will take a longer time. (729,000)
✓ If X, it will take longer. (45.8 million)

(Note that less (short adjective) often sounds questionable; not as (short adjective) is better.)
? If Y, it will take a less long time. (0)
? If Y, it will take less long. (8,140)
✓ If Y, it will not take as long a time. (0, so maybe my judgment is wrong)
✓ If Y, it will not take as long. (1.1 million)

Superlative:
✓ Z took the longest time.
✓ Z took the longest.

Seeing how the other two answers are reluctant to say that "It took long" is fine, I think that I should rather post this as answer.

'Long' is an adjective as well as an adverb. So, "It took long" is perfectly fine because the "long" acts as an adverb in that sentence. Some reference: http://merriam-webster.com/dictionary/long%5B2%5D

Therefore:

• This took long. -- is fine
• If we do X, it will take longer. -- is fine too
• If we do Y, it will take less long. -- is strange

As for the last one (less long), imagine you use "long" to describe a physical object, say a stick. If stick A is longer than stick B, how would you say?:

Stick B is .... than stick A.

It should instantaneously come to you that you need to use "shorter" there. So why wouldn't you use "shorter" with time as well?

• If we do Y, it will take shorter time. or just If we do Y, it will take shorter.

(According to http://www.merriam-webster.com/dictionary/short%5B2%5D, "short" can act as an adverb like "long" does)