I do like the fact that Genasi heritage and genetics is a little more fluid, and it's kept the mixed origins of Genasi in mind (unlike the Tieflings). And that 4e genasi powers are a lot more useful and evocative of an elemental nature than many of the previous edition genasi powers (let's see lower water vs. turning into a stream water). The personality descriptions are almost identical to the 4 genasi races of the past. Excluding the joke in one of the Planescape books about the slow and ponderous nature of Earth Genasi.
What I don't like that they've made all Genasi have those elemental lines on their body. It's something I definitely find wrong with how they've handled Genasi. While it's something easy to houserule, going back to the varied appearances based on elemental 'manifestations' from subtle to obvious. It's not something I like, as it seems to be pushing rather bad artistic depictions, like those in this article which I certainly don't like. I'd like the genasi to only have lines if their players want them to have it, otherwise they can have anything from flowing hair to webbed feet, or vestigal tentacles in the hair or brown leathery skin.
If there's another to do with Genasi, it's to come up with new 'manifestations' vaguely based on other 'energy types' and the para and quasi-elemental planes such as Radiantsoul, Frostsoul, Causticsoul, and so on as long as they make sense and don't try too hard on filling the old slots in as many have done before.