癖のある would be more towards "quirky" in English. The expression 癖のある by itself has no significant tone of being positive or negative.
Less quirk than quirky
The word "quirk" seems to carry other meanings beyond its adjective "quirky" according to Collins English Dictionary. American English (not quoted) has similar meanings but takes different orders of priority compared to British English (quoted below).
an individual pecularity of character; (○ 癖のある)
an unexpected twist or turn; (✕ 癖のある)
a continuous groove in an architectural moulding; (✕ 癖のある)
a flourish, as in handwriting; (△ 癖のある)
I have added notes in the brackets to describe compatibility of the expression against each meaning, such that
○ 癖のある: commonly used;
△ 癖のある: sometimes used;
✕ 癖のある: not used or not found.
Positive, negative, neither
Does the expression have positive or negative connotation? This thread on Yomiuri Online had asked a very similar question to that: what kind of person is described as 癖のある, or what does 癖のある人 mean literally.
And the earliest answer contributed by 秋の温泉 dated 2011年10月21日 11:56 had replied as following (partially quoted).
The relevant point translates to "Not a bad person. However, the person is neither good, of which anyone would describe as being a fine exemplary of virtue (moderate, kind, good manner, etc.)". So it could be positive or negative, but it's neither to begin with.
Perfect example (added 2017.03.16)
The following sentences make use of the expression 癖のある and put the expression in different tones to make sense in this answer.
(1) Sometimes, I would be bothered by quirky user who don't leave any comment while a downvote has been made.
In the first sentence, 癖のある would be translated as "quirky" to describe the peculiar behaviour of user. This expression by itself doesn't mean positive or negative. It is neither. The following sentence changes the expression into a different tone.
(2) It is a user's privilege to cast a downvote however, given that comment was not available, there is no clue to make revision thus, the user is also said to have a bad habit.
In the second sentence, 癖のある is translated as "have a habit" due to the expression is preceded by the adjective 悪い "bad". When combined into a single expression, 悪い癖のある is now translated as "have a bad habit". As a result, this expression has a negative tone.
Therefore, depending on how the expression is used in a sentence, the tone can be positive, negative, or neither.