Call me a cynic, or maybe just overly cautious, but I won't completely trust a product unless it has proven to be benign, or I've verified it to perform like it is specified.
All of the remarks about USB, voltage, and amperage about are good, and true, but leaves out whether a particular product design is actually good, and safe.
The popular product trend now is to integrate USB ports into power strips, and other mains distribution gadgets.
But there is a certain school of thought which believes in the mantra of "Jack of all trades, master of none" that makes me question how two different products that are sold for roughly the same cost separately can still be sold for not much more when they are combined? Are there hidden compromises?
What is the quality of the circuit that drops the mains voltage to 5V? How well is that voltage regulated, and how much noise does it have? How much separation is there between the high- and low-voltage circuitry and is it sufficient to be safe? Does it produce excessive radio interference?
(One example--there have been instances where poorly-made USB car adapters have interfered with a vehicle's tire pressure warning system, causing false warning lights)
Those questions apply equally to both traditional mains adapters, as well as these dual-purpose power strips, or any electrical product, for that matter.
In theory, the CE marking on the example above should provide some assurance, but markings can be faked, and many products on the market are plastered with a lot of them to make them appear more legitimate, but may lack the optional, but valuable markings that are truly relevant to their performance or safety.
A RoHS marking, which commonly appears on many electrical gadgets, is only meant to signify that it is made with fewer hazardous substances. A marking relating to recyclability serves only as a warning to properly dispose of the product. Neither address the certifications required for things like radio interference (FCC), or safety (UL, ETL, TÜV, etc.).
I'm not familiar with the OP's product in particular. If may in fact be well-designed and perfectly safe.
But one should be cognizant that there is a lot of junk on the market which may not be, so exercise some skepticism, if not caution.