Safer, faster to pay back and, as my sister has noted, deals with holiday delays. Modification to the new union contract in negotiations to allow it to happen.
(That may be behind a paywall. Sorry.)
Summary of what other states are doing.
"Toll authorities have spent two decades refining issues such as billing rental car drivers and collecting from people who ignore bills, especially across state lines, with mixed success, Samuel said, but the benefits far outweigh complications.
“It’s pretty clear that it is a more economical way of collecting tolls . . . than paying people to sit in a tollbooth,” said Samuel, likening toll collectors to elevator operators. “It’s just one of those jobs that’s not really needed anymore.”"
This one raises the "specter" of tolls on currently "free" roads. I don't like that frame. Someone is paying for those roads; I'd just as soon have more of the cost be paid by the people who actually use the roads.
Few if any of these articles are directly addressing "Big Brother" concerns -- but that crops up reliably in the comments. I seem to recall reading something in the LA Times a while back about a guy who was wrongly convicted of something-or-other because of the testimony of a truly awful woman, and who eventually cleared himself in part because of some electronic toll records.
ETA: This isn't about Massachusetts; it's about rental cars and plate-recognition tolls, however.
Some complaints about PlatePass in my area over on FlyerTalk:
Florida and Rental Cars:
Consumer Reports advice on how to deal with the markup of toll collection systems on rental cars, from 2011:
How to avoid rental toll markups when crossing Golden Gate:
More about possible future tolling in Massachusetts, those scofflaws (!!) in Connecticut, a fascinating glimpse in bi/multi-lateral agreements to collect tolls from drivers across state lines . . .