挺好的。说点个人意见

1. 既然用了middle child, brethren似可翻成兄弟产品。
2. slew 你翻得很对，在这里就是“大量”的意思。

Let's start off with the obvious, the nano is considerably smaller than its predecessor and now rivals the shuffle as the smallest iPod and the touch as one of the coolest and “funnest” iPods ever made.
****shuffle, touch都是ipod兄弟产品。这里的意思是，nano体积小到与shuffle不相上下；在时髦好玩方面又可与touch媲美。

It weighs close to nothing （21g）
****体重轻到可忽略不计（21克）

A series of dots at the bottom of the screen indicate how many pages there are and which page you are currently viewing whether you're just navigating the menu system or within an app like Fitness or FM radio.
****这句的翻译好像有点问题。 意思应该是: 不论你是在浏览菜单系统还是处于健身或调频收音机的应用程序中，屏幕底部都会有一系列点显示总页数以及当前的页数。

It doesn't appear as though “On the Go” playlist creation is possible, though.
****这里的appear应该是貌似的意思：）
as though: as if

but its small stature and intuitive UI make it stand out from the rest.
****stand out from the rest可翻成“在同类产品中脱颖而出”