I bought this phone for my eldest son in April and have also bought a second one for my youngest son in May as we all thought Xperia E was a good buy. This purchase was a bit of leap into the unknown as its new and there are very few reviews about it, but based on the specification I couldn't find anything better for the money. This is a budget phone so don't expect stunning results from the camera but otherwise the phone performs excellently on web browsing, internet text chat and calls. Works well on Wi-Fi and connects with my home Netgear router and Belkin Wi-Fi router that I have configure to operate as an access point, also works well with the wireless router supplied by TalkTalk. The Xperia E requires a standard size SIM card and our phones are on the 3 and O2 networks. The GPS works well and have installed a free app "mapmyride" that provides mileage data and calories consumed when out cycling.
The phone can also be used as a Wi-Fi hotspot (Mi-Fi) i.e. the 3G provides the internet connection and you connect other devices like a tablet or laptop via their wireless network adapter to access the internet. This is very useful if you want to use your tablet on the move but you'll need a mobile tethering feature in you mobile contract to enable you to use this.
There is also a preloaded barcode reader app NeoReader.
I have also purchased a SanDisk microSDHC Ultra 16GB, class 10, UHS-I, 30MB/sec, + SD adapter, Mobile; £9.99 from Amazon. This memory card works as you would expect in this phone; no issues.
You may find this review link useful if you're considering buying this phone http://blog.clove.co.uk/2013/05/27/sony-xperia-e-review/
For you techies out there you might be interested in this article showing the evaluation of the Firefox OS on the Xperia E.