Is the Gucci YA157438 a good everyday watch?

Yes, if you want a dressy quartz watch. It is accurate and low-maintenance, but it is not built for sports or heavy water exposure.

Does it have a mechanical movement?

No. It runs on a quartz movement, which is more accurate and needs only occasional battery changes.

Can I wear it swimming?

Treat it as a dress watch. Gucci's fashion watches are generally rated for light splashes only, not swimming or showering.

Is it worth it over a non-designer quartz watch?

You are paying for the Gucci name and the pink design. A plain quartz watch tells time just as well for far less; buy this for the look and the brand.

What should I check before buying?

Confirm the case size suits your wrist and that the strap type matches your preference. Dress watches like this wear best when the case sits flat and slim.