Does "effusive" have a negative connotation?
Solution 1:
No. Effusive is not negative, it has a positive connotation to it. 'He was very effusive in his praise of the features.' is fine.
effusive
adjective demonstrative, enthusiastic, lavish, extravagant, overflowing, gushing, exuberant, expansive, ebullient, free-flowing, unrestrained, talkative, fulsome, profuse, unreserved
He was effusive in his praise of the General.
Also,
This ngram for effusive in his praise and effusive praise shows the expressions are on well-trodden territory:
Solution 2:
Personally, I've never seen "effusive" used negatively. "Gushy", on the other hand, has always implied that it's too much.