Can the word "dabble" be used in a positive sense?
A true "master of all trades", he has dabbled in several fields & contributed to numerous scientific advances.
Mostly, it just depends on how one extends or qualifies the impact of dabbling. Dabbling seems to have a certain antecedent>consequent structure to it that implies the positive/negative; i.e. with both example phrases above there is no +/- value until the "and..." statement created one.
In BE it is a positive sense - to dabble in something is gentlemanly.
(The above may account for Britain's expected performance in a certain sporting event to be held in London in 2012)