She was pretty much useless. Most of the places she sent us didn't match our criteria very well, and quite a few were above where we wanted to spend. As each day went by and we nixxed place after place she clearly de-prioritized us in her work (I'm assuming she was working with multiple other people who were looking for places) and became less responsive.
At the end of the day I had to do my own hunt and fly up a second time to look at places over a weekend to find something.
And that's a paid agent from a large moving corp. I do wonder if a (more expensive) boutique agent would have been more effective but honestly having worked in real estate I consider them all at the same level as used car salesmen anyway.
As an aside I also tried to automate my apartment hunt. The main thing that matters in NYC is time to respond. Unfortunately Zillow, StreetEasy, etc are not very easy to automate on the messaging side due to bot countermeasures. It was an incredibly time consuming, manual process. Happily found a great place though.
In NYC specifically, there are agencies that make most of their business from renter-side representation. You can find the good ones easily on the usual review sites.
In Melbourne Australia, what I have seen is that rental agents are different and the real estate agents are different although they work for the same company.
As someone else in this thread noted, the landlord often hires an agent because they don't want to deal with the tidal wave of crap that comes from dealing with applicants. That person gets paid, obviously, and the landlord isn't the one paying them. That's the rate you're talking about here. These people are not incentivized to provide good service to the renter, and typically don't. They suck.
Higher-end buildings often have in-house agents (again: you're paying for this, whether you realize it or not), and these are called "no fee" buildings. But an increasing number of places don't have either, and just provide access to professional renter's agents instead of listing publicly. Or they do list publicly, and barely respond to the tidal wave of yahoos, knowing that motivated renters hire an agent. YMMV.