Is "hell of a" positive or negative?

I find it a very curious thing that the phrase "hell of a" seems to be suitable to describe both good and bad things.

e.g.

It was a great party. We had a hell of a time.

vs

We sold the house eventually. But we had a hell of a time.

I certainly hear it more commonly used as in the first instance, but I imagine that this is a regional thing. But I wonder which sense came first. What is the etymology of the phrase?

And, with this in mind, how should I interpret a sentence with very little context?

e.g.

We had a hell of a time when we visited my parents over Christmas.

The phrase "a hell of a time" contains two idioms. "A hell of" and "a time".

As other answers have said "a hell of" just emphasises the strength of something.

That man has a hell of a cheek

She has a hell of a talent

He has a hell of a big nose

... and so on.

"A time" often refers to a period that was interesting in some unspecified way, especially when preceded with a strengthening adjective.

He had quite a time during his illness

What a time we had on holiday!

Put them together, and you have:

We had a hell of a time.

There is nothing in the sentence to say whether they had a hell of a good time, a hell of an exciting time, a hell of a bad time, a hell of a dreary time. All of that is to be inferred from context.

And perhaps the speaker doesn't want you to know the truth.

Related: if you say "I had a hellish time", that's always bad.

It refers to the extremity of goodness or badness.