I'm not sure how strictly the line is being enforced, but I can tell you there have been no problems or confusion with it during the sessions I've played at Rivers this month. I know there are arguments out there that betting lines enforced too rigidly can lead to angle-shooting, but I've always felt a table with a line is better than one without, so long as as the rules for what constitutes a bet and what constitutes a muck are enforced clearly and consistently by dealers.
The new betting lines also mean that the casino's bizarre, much-derided "cut rule" is officially a thing of the past. I emailed room manager Mike Chapman today for confirmation that the rule was abandoned, and this is the reply he sent:
"We allow for cutting of the chips in one unbroken motion. If you hesitate, it will constitute a stoppage of the bet. As always, we encourage you to verbalize your bet to eliminate any confusion."
That's pretty much a perfect answer, as any long pause while cutting chips essentially turns it into a string bet. But at least players can now cut out a proper bet without the dealer declaring that their first cut was the bet just because it was made a fraction of an inch past their hole cards. The cut rule was always silly and created more problems that it solved. I don't expect anyone will much miss it.