I have Omnium cranks on one of my track bikes. Not bad, but nothing spectacular about them. Worth noting though is they have slightly thicker arms than usual and with some chainrings you don’t get much thread engaged on the chainring bolts. Numerous cases of people having issues with them coming apart while racing, which is not pretty.
Fix is simple:
Buy some high quality stainless steel double chainring bolts and use the fronts of these, with the backs from singles (preferably dura ace track bolts). That way you get plenty of engagement. Bonus pro tip – tiny bit of superglue on the back bolts stops them falling out the cranks as much when changing gearing.