I’ve done clutches, TBE on FWD & AWD, suspension, brakes, engine/transmission mounts, FMIC...basically all of the standard mods plus a ton of fabrication on my QuickJack.
It’s a great tool and mines DC powered so I can literally take it anywhere (track days, friends house, wherever) and it’ll run off the cars battery.
With that said I’m buying a two post lift, but for most people that’s not an option. I feel like 90% of people here would be happy with a QJ.
As for safety and stability as mentioned above just use common sense and do your routine maintenance and checks on it like anything else. I stack both blocks basically every time I’ve used it, with no issues in that respect. Even my wife’s Kia Sorento (replaced by a Suburban now) was no problem for the 5000# model. I’d never put the Suburban on it, but my two post will handle it no problem.
I agree the QJ is great for almost everything...with the exclusion of the DP