I have used Fritzing and like it but there has always been a “not quite right” issue … no simulation of the circuit.
I teach to young children who are starting in Electronics and used Fritzing to show breadboarding and design.
They cannot test their creations without immediately going to hardware and then going back and making changes to the design … back and forth .
Beginners are put off.
The designs are not complex but we have needed a simulation tool.
Yes Fritzing Definitively needs a simulator … Even if its just a start to a fully fledged one or can check circuits up to a certain level of complexity.
Now I am using Autodesk 123D free breadboard prototyping webpage that allows a circuit to be built then tested. It may only be for simpler ones at the moment but they are complex enough for many projects and once built a circuit can be tested.
Many things that are in Fritzing would help like rewiring by dragging a wire to another point rather than deleting the wire and starting again, having curved wires and more control BUT the simulation ability makes up for the lack. What its missing will probably be added as it matures. I can display voltages currents and oscilloscope traces with virtual multimeters and tools. Learning students take to it easily.
I have used Arduino with varied code and it works, up to quite complex ones. It will only improve.
Fritzing will gradually bleed users until it is forced by necessity to add a simulator option of some sort, then may be too late and have a strong competitor.
Or it will die … anyone heard of Netscape, Lotus 123, Nokia ?