We booked our own...
I believe the TA will help with that, but I wouldn't think it's there #1 priority. They are interested in booking your trip, and taking their commision, after that is done, they will help where they can, but when they get around to it.
As well, if you tell the TA you want (for instance) Le'Cellier at 6:00 pm on a certain date, if they try to book, and find out that it is not available at 6:00, but they do have 5:15 or 7:00, your TA may not know your personal preference, (whereas you can make the best decision for yourself on the spot).
I like the control - and when you do get the ADR you want, it's kind of a personal victory, something to enjoy yourself.
With all that said, I don't believe they have toll free 1-800's for dining, so without a good LD plan, you may be on hold for up to 30 mins at peak times, in which case let your TA incure those charges.