I don't have very good memories of these. Quite apart from the fact that I was hurt by inexpertly piloted examples whilst marshalling on numerous occasions, they always seemed very agricultural. I had friends who owned them and they were always complaining about design flaws such as the bumper mounting points that used to break easily and the driveshafts that used to fall out. Anything warmer than a very mild modified motor would chew up the drivetrain, too. The horrible crucnching sound of Boomerang (or more rarely, Super Sabre) returning to driver leaving a trail of broken parts and gears behind it was a common one when I was younger.
That said, many of its problems could be put down to poor maintenance by inexperienced and impatient drivers, but since that was its main target market, that was always going to happen. It's Marui rival, the Ninja, never seemed to have the same issues, despite having to work under similar conditions. The Ninja drivetrain always sounded 'tighter', which implies that the Boomerang/Super Sabre gearboxes had more slop built into them, which won't have helped their cause.
Tamiya addressed a lot of these issues with the next generation Thundershot/Thunder Dragon/Fire Dragon/Terra Scorcher series, which was a much better thought out chassis.
They also didn't have the utterly pointless and ineffectual Boomerang rear wing, which acted like a big airbrake and contributed nothing to the car's aerodynamic profile except drag.