There's lots to like about the HTC One S.
Size-wise, I'm a fan of pocket-sized phones, and the One S fits in my jeans more comfortably than its larger cousin, the One X.
It may not have an external storage card, but 16GB is a generous amount of internal space.
Unless you are big on multimedia content, and store lots of movies and games on your phone, you won't miss the extra 0.4 inches and faster processing speed of the One X.
Both phones have the 8-megapixel f2.0 rear camera, and the interface is smooth and intuitive. Users of older versions of HTC Sense may need a little more time to adjust to some of the quirks of HTC Sense 4.0 like the drag-and-drop interface for widgets and shortcuts, but it's not a big issue.
If you're not splashing out for a larger screen and faster processor on your smartphone, the HTC One S is a nice upgrade over an introductory smartphone.