That looks like a decent antenna, indeed. Probably better than the chip antenna, and probably worse than a specifically designed 2.4GHz antenna.
I’d pour some hot glue over the soldered end, for mechanical resistance. I can’t tell how flexible that cable is, but the last thing you want is for it to take out the pad on the PCB. Try not to cover the u.FL connector with glue, in case you want to use it later.