When is a common emitter amplifier a good idea?
The TIP127 is there to lend some grunt brute force so that currents greater than about 50 mA can easily be created at the output. Because the lower op amp "measures" that current and is in a negative feedback loop with the op amp that drives the transistor, the non linearities of the transistor are of no great consequence.

Stability can be a significant problem on circuits like this but, C1 reduces the loop gain at high frequencies ensuring phase margin never drops close to the oscillation point.