I view Twitter as neither positive nor negative. I view it as inevitable. It's one of a long line of things that can have their positives and negatives argued:
guns, nuclear energy/weapons, genetic engineering, combustion engine, and thousands upon thousands more.
If something can be invented/marketed/used, it will be. Whining about it does nothing to change it.
The real issue I see wrt to Twitter specifically is the deception behind it as being some sort of open format. It's not. It's just a company doing predictable things to bolster its bottom line and market share. It tries to keep competitors at bay.
It gets to do this in unusual ways compared to older companies. The past two POTUS' have given them free advertising daily. Imagine if JFK always had a can of Coke while speaking. Would that hurt Pepsi or potential future Pepsis? Beverages are one thing but centralized messaging carries a lot more leverage.