Can this circuit be used as a +/- 5V split power supply?

 

Yes, but note that the negative rail will be a slightly lower voltage than the positive depending on how much current you draw.

 

Can this circuit be used as a +/- 5V split power supply?

Yes. That's what the chip is designed to do.

Depending on how much load current the chip will be required to supply, you might want to connect pin 1 to pin 8 to boost the internal oscillator frequency, lowering the chip's effective output resistance and reducing the voltage droop under load. Consult the data sheet.

 

Yes, but note that the negative rail will be a slightly lower voltage than the positive depending on how much current you draw.

I was thinking of using it to power three 7-segment displays and their drivers. How slight is 'slightly lower'? Is there any improved version of a circuit which uses LM2662/3 ?

 

The datasheet tells you how to calculate the output resistance in terms of the oscillator frequency and the capacitor value so you can know how much the output will drop.

It shouldn't be critical for those displays.

 

How much current does the display and drivers require (all segments on)?

 

The datasheet tells you how to calculate the output resistance in terms of the oscillator frequency and the capacitor value so you can know how much the output will drop.

It shouldn't be critical for those displays.

The display draws 25mA and at 150kHz the voltage drop is 0.1 V from what I can see so it looks OK.