For navigation it's probably as good as any but for those of us close to traffic hotspots it's mandatory
London's M25 is a notorious 'car park' at times, as is the M4 near Heathrow and accurate traffic is essential
When I used to leave Woking, about 20 years ago, I would consult the then Trafficmaster display as I headed for J11, Chertsey. It would often show that the tail of the clockwise traffic was currently J15, Heathrow, where I used to turn off, so no problem.
I kept an eye on the traffic when approaching J11 and often it would have updated to show the tail as now J14, Heathrow Terminal 4, again, no real problem.
However, quite often, I would join the M25 clockwise sliproad only to be met with a jam or hit the tail of the jam at J12, M3, 10 miles sooner than was being reported.
Then I got a standalone Garmin with Inrix live traffic that covered all roads, not just motorways and major A roads as covered by Trafficmaster.
Inrix via Garmin updated about every 60 to 90 seconds and that showed the correct tail of the jam so I could divert. And while I had diverted the built in Trafficmaster was still showing all clear.
My diversion route involved driving under the M25 near J13 and I could see the stationary traffic so I knew Trafficmaster was wrong due to it's reporting delay
Move forward 10 years from my standalone Garmin and I now have Google Maps on the headunit which also has correct traffic and no need for wiring a standalone Garmin
So for some scenarios it is hopeless without up-ahead road conditions