I currently use the Ryobi One+ 18v tool system, however my experience with their tools is mixed. I find in cases where there are a number of options of a given tool such as a drill the top of the range ones are good, however if there is a singular option them mileage may vary.
Because of this I am looking at getting into another system, I don't think I will move off all my Ryobi stuff anytime soon though.
What other systems do people find provide a good range of options with a higher standard than Ryobi but without a huge price premium. The guy at the local Bunnings pointed me towards AEG but that is just one opinion.
Use wise I am a home based hobbyist so the tools probably get heavier use than DIY but not as much as a tradie.