Have flown from Mildura to Melbourne several times. Service onboard is reasonable, no frills, and about what you might expect from a regional airline. I have had no issues with that.
The main problem is the frequency and magnitude of delays. Unfortunately the delays are frequent and usually an hour or so. This time the delay was bad enough that I missed several other appointments and had to reschedule them, costing a fortune in terms of having to rebook several of them.
I'd generally avoid them unless delays are not a concern. Unfortunately they seem to have a monopoly with regard to takeoff and landing slots in Mildura airpirt - neither Virgin or Qantas has the evening slots after 5.30pm, which lets you fly after work.