1) Social network
Connection to social networks is an essential feature that any smartphone should have and the apps for Facebook, LINE and whatsapp are decent enough. Previously I used Nokia Lumia 610, and I find 710 to be faster and more efficient.
One grouch I have is the inability to upload photos by the thousands. Okay, I exaggerate but mass photo upload is not provided. Direct upload to SkyDrive is provided as a default function, so do utilize this cloud concept heavily if you prefer to move the pictures and videos out ASAP. You may upload other file types here as well.
SkyDrive is the primary option to upload and store files in a cloud, but you may opt for Dropbox if you prefer. SkyDrive is linked to your Microsoft/MSN account so it's easy to use and to organize the files.
Adobe reader is provided so you can open and save pdf files to your phone. However, you can only read the pdf files later so forget about attaching the file to your email. If you like reading, you can install an epub reader, like Freda. Again, SkyDrive is useful for storage of epub files that you may access via Freda for easy reading on your phone. The ad-free version is good enough, just take a sec to click the ad and you're good to go.
I'm an avid user of Media Downloader; together with the YouTube app, I've a collection of funny videos at my fingertips. You may also download music (however I've not tried it yet). The Windows 8 version allows synchronization of downloaded media between the phone and PC.
One feature that's heavily argued as either a specificity or a limitation is the dependence on Zune. Similar to iTunes synchronization with Apple products, you can only transfer files between PC and phone via Zune. I suppose its Microsoft's strategy to battle piracy but so far, so good. However Zune is now merged with xBox so you'll have to download the software from xBox and you can access music from same.
The gang's all here: Gmail, Yahoo Mail, and certainly Hotmail can be installed on the phone. You can sync your contacts so you can directly email them if you wish. For someone with 6 email addresses, this is a handy feature, however typical.
I admit I'm a pepperazzi, so basic photo editing is a must for me. I've installed Photo Studio (cropping, rotation, etc), Phototastic (comes with a myriad of frames, photo combination, hues and color editing). However, Microsoft and Nokia has each produced fascinating apps, namely Photosynth (create panorama pictures) and Cinemagraph (creaye animated gif files from still photos). Nokia has created #2InstaWithLove for users who pine for Instagram.
Microsoft and Nokia frequently provide updates as well as produce new and interesting apps for the Windows phone users. You can sign up for Nokia Beta Labs that produce new "beta" apps for Windows phone. In my opinion, you define the kind of apps you're most likely to use, hence your smartphone choice should reflect your interests and practicality.
Feel free to share your experience and opinions :)