Gravity is a rarity among Symbian applications. It has a UI that not only looks good, but also works great. It is fast and comes with massive loads of features. What started out as a simply Twitter client, the sole developer at Mobileways.de has implemented support for Google Reader, Foursquare, Facebook and the open source StatusNet, with varying degree of success.
Considering how backwards Symbian is supposed to be (according to American blogs anyway), and how there are virtually zero competition on the platform, the number of features on Gravity is quite a feat. The sheer number of features, it's stableness and speed, easily makes Gravity one of the best mobile social network clients on any platform. And I say that with a straight face.
At a time when Nokia is urging developers to code in 'code once, deploy everywhere' Qt, Gravity is still reassuringly native. I've nothing against Qt, but so far none of the Qt based applications I've seen has convinced me it is better than native. Gravity is compatible with S60v3 and all modern Symbian touchscreen devices from Samsung's abandoned at birth Omnia HD to Sony Ericsson's cute Vivaz and Nokia's 'flagship' N8.
Let's begin with Twitter, as this is what Gravity was designed for. Gravity has almost all the features that I could ever want from a mobile Twitter client. It supports both native and old-style retweets, geolocation tagging of tweets, follow/unfollow, direct message (with threaded UI), the creation and management of lists, uploading images to popular image sharing sites (TwitPic, Flickr etc.), alert, multiple accounts, draft and schedule posts, homescreen widget, notification (in both screensaver on Symbian^3 devices, as well as audible/vibration) and much more.
There are a couple of features I would like to see added. For example an alert when someone follows, filters and the ability to open URLs to Opera Mobile rather than Symbian's native Web browser. Speaking of URLs, you can also set Gravity to save URLs to Instapaper and other services to read it later, a useful alternative to using the favourites function to bookmark posts to read later.
The Foursquare client is as basic as it goes. It only allows check-ins and shouts (to Twitter and/or Facebook - provided you have your Foursquare account is linked to them). There are no supports for leaving and viewing tips, nor is the ability to delete previous check-ins from the history present.
The most curious absence is the lack of Specials, a Foursquare feature that allows participants to reward check-ins to users, so don't go deleting that amateurish official Foursquare Symbian client just yet. Having said that if all you want to do is check-in or shout, Gravity is perfect.
If you are a Facebook user, you will be pleased to know that Gravity supports pretty much most of the important features of Mark Zuckerberg's Friendster rip-off, including Messages (in threaded conversation view), notifications (no friend requests here), News Feed and Status Updates, including replies. It isn't a Facebook mobile client replacement, offering even less than Facebook's touchscreen mobile website. But it is indispensable if all you want is a quick glance on what your Facebook friends are up to, post a status update or reply.
A built-in RSS reader in the form of Google Reader is the next major feature of Gravity worth writing about. This is pretty basic, but at least it has all the essential functions one would normally need form a newsreader software. Like the Twitter bit of Gravity, URLs can be posted to Delicious or added to Instapaper or Read-it-Later. There is an option to easily tweet the post as well.
In an age of 99p mobile apps, Gravity isn't cheap (£8 via the Ovi Store), and that's before taking into account the amount of good freeware social network clients you can get on competing platforms like Android and iOS. But if you have a Symbian phone, and you need a powerful Twitter application then Gravity is your answer. You could do a lot worse with £8 anyway.
I also have a relatively modern Android phone (with around ten Twitter clients installed!), and my girlfriend has an iPod Touch 4G which she tethers wirelessly to her ageing Nokia none-touch smartphone, and both of us always fall back to Gravity simply because we both think it is the most effective mobile Twitter application available on any mobile platforms.