Not at all (at least for me on a 100mbit connection with the Pi 3B+). I've read you could even use a pizero if you don't care about the Web interface being all that snappy.
> Any weird sites that don’t work with it running?
You set your own blocklists so you can choose how permissive you want to be. I have something like 1MM blacklisted URLs and rarely find sites to be completely broken. It's easy to temporarily pause the blocker, or add a single domain to the whitelist.
> How much better is it than something like ublock origin?
uBlock origin has the advantage of hiding content directly from the page, whereas pihole tends to leave a greyed out box where the ad used to be. I tend to use both at the same time anyway.
I’m currently trying to phase off my dependence on them.
Gotta wonder what kind of ad tracking/targeting they do based on DNS lookups you send them
Does the hardware limitations of the pi mess with download or upload speeds at all?
Any weird sites that don’t work with it running?
How much better is it than something like ublock origin?