Advertising is inherently at odds with productivity (ads waste your time) and potentially privacy (for better ad targeting), so I wouldn't recommend it.
Under the hood it's just a reskinned Chromium so the battery life & performance concerns remain.
As for Chromium's performance, I think it'll improve over time as MS started using it for their Edge browser and are committed to improve performance and battery life.
They've blogged about this in detail. One recent post was : https://brave.com/accurately-predicting-ad-blocker-savings/.
Stating that they're simply an advertising company misses a significant amount of innovative work they're doing in-browser too.
They're building a new business model and infrastructure that is diametrically opposed to the current surveillance capitalism model, and this infrastructure can replace donations, sponsorship, advertising and subscription models in a way that reduces transaction friction significantly, and could very likely challenge a significant number of powerful incumbents.
They are an advertising company at heart.