Redbulls & other energy drinks have B vitamins and such that synergies with the caffeine to make the energy effect stronger. So even though your drinking 70mg of caffeine in a redbull, it feels a lot stronger.
Drinks such as coffee have a ton of caffeine in comparison. A cup of coffee has around ~200mg of caffeine, while yerba mate drinks have around ~70mg: http://guayaki.com/caffeine_meter.html
So drinking yerba mate is a lot like drinking tea as far as the caffeine experience goes.
Unfortunately, it seems that B vitamins do not 'synergize' with caffeine in an appreciable way, per an article from the LA times in 2008. Caffeine does have a 'negative' effect on circulating B vitamin percentage, but I could only find one study from 2008 about it, and it's not unhealthy. As is, the B vitamins with coffee really only seem to help in the elderly.
That said, yeah, mate is pretty mild in terms of caffeine content.
Drinks such as coffee have a ton of caffeine in comparison. A cup of coffee has around ~200mg of caffeine, while yerba mate drinks have around ~70mg: http://guayaki.com/caffeine_meter.html
So drinking yerba mate is a lot like drinking tea as far as the caffeine experience goes.