Best feature over other battery packs I have tried is that you can turn off the alert:

The feature I like best is its auto shut down

I don't think the non-replaceable battery is a dealbreaker for that reason--and surge protectors don't last forever, anyway, so at some point you probably will want to replace the whole thing if that feature is valuable.

The best feature is by pressing the silver button twice quickly you can shut off the alarm that goes off when the power shuts down