The best adblocker for Firefox and there is very little reason to use anything else. It is open source, has blocklist customization, supports blocking annoyances and trackers as well as ads and it will never ask for or require micro-transactions.

Most recent update has caused numerous websites to no longer correctly function for me. I don't know if this is the same for other users, nor the extent of what sites are affected.
Youtube does not load video pages on left click, it requires a "New window" or "refresh page" to play a video you click on. Mild nuisance.
Bigger problem: Email is failing to load and I must disable/re-enable uBlock to view anything. Probably other problems. If this were my first impression of your extension, I would judge it very harshly. Only because I have had very good experiences do I not feel this way now.

best blocker ever!

Ublock is amazing. I haven't seen an ad in so long! It makes my whole experience safer. It's quite simple to customise (I've never used the advanced settings though as I am definitely not an advanced user). I appreciate this extension and the people who make the filter lists so much.

Haven't seen an ad, or a website detecting I have an adblocker. The only thing I've seen is a website saying "an ad used to be here", but those might've just been placed behind the ad and not a sign of the adblocker being detected.
Youtube does sometimes detect you have an adblocker, but it's always fixed within a week. Even then, them purposely making your video load 5 seconds slower is less annoying than a 30 second ad.