IM+ is an IM client with push notification support for 10 networks, including Twitter. I use AIM, Facebook, and Twitter, so these are the only networks that influence this review.
The design of IM+ is nice and intuitive. The bottom toolbar has tabs for contacts, inbox, favorites, status, and more. Under the contacts tab you will find find a list of your contacts organized by account, group name, or no group (selected in settings). If no group organization is chosen, then your contact list will by organized alphabetically based on availability. So, the top of your list will show available contacts, then idle or away contacts. At the bottom, offline contacts are treated as a separate group. There is an option to have offline contacts hidden.
Tapping a contact will open a chat window with that contact. If there is a previous conversation stored on IM+, then the window will include that conversation.
To the right of of every contact, there is an "i" to find more information. Tapping this will display the status of the contact, their user ID, as well as the ability to add to favorites, rename, and delete (provided that the IM service associated with the contact allows).
The inbox contains all current and past conversations. If a twitter account is enabled, then @replies and direct messages are treated as their own separate conversations. It is not possible to have twitter conversations treated as a conversation in IM+; only incoming messages are shown in the @reply and DM threads. Conversations can be easily deleted from the inbox with a tap of the edit button.
When writing a message, there is a smiley face on the left and a keyboard on the right of the text field. Tapping the smiley gives a list of symbols (mostly smileys) that you can insert into the message. Be careful with these though, if the receiving client doesn't recognize a symbol, it will be displayed in text form, or worse, a smiley face with some symbols attached.
Tapping the keyboard symbol collapses the keyboard and the smiley face converts to an upload symbol. From here you can send your location, a picture, or voice message. You have to be careful with this too because once you make a choice, it sends without confirmation. This is a major problem, in my opinion. I attempted to send a DM tweet with my location and IM+ ignored the text and sent my location as a public tweet! I'm just glad I was at Starbucks and not my house! This also means that text cannot be included with any media type. All media gets sent as a link. Pictures and voice memos are hosted by IM+ and GPS locations send a link to GPSed.com. It would be nice if the link launched Google maps on an iPhone so the recipient could quickly get directions, but it doesn't.
All links are opened in the built-in browser of IM+. This browser is very cool as it not only allows for reading and navigating through websites provided by links, but you can use it to visit any site by typing the web address into the text field at the top. This is very convenient for those times someone starts an IM conversation when browsing Safari. Just copy the URL before exiting Safari, launch IM+, paste the URL into the browser and quickly tab between conversation and browser. When your conversation is over, just tap the globe at the upper right of the browser to open the current page in Safari. Awesome.
Next is the favorites tab. This is simply a list of contacts that have been marked as favorites. You can add or delete contacts from this list and see more information about them, just as in the contact list.
The status tab is where you can choose your status message (for supporting networks). There are 6 options, Online, On iPhone with IM+, I am here (with link to GPS location), Away, Invisible, and Offline.
The more tab gives access to your accounts, settings, and in-app web browser.
IM+ is not intended to be used as a primary Twitter client, but makes for a great secondary client. It's convenient to be able to access twitter while holding an IM conversation without having to go back and forth between two apps. Reading tweets on IM+ goes against the conventional style of most recent on top, but this doesn't bother me because I find uniformity within an app to be important and it doesn't make sense for normal IM to read like Twitter.
What makes Twitter so great on IM+ is of course push notification. All DMs and @mentions get pushed within 4 minutes of being sent. Ideally, they would arrive faster, but 4 minutes isn't too bad. The problem with Twitter push on IM+ is that there is no way to choose what you want pushed. It is also a little glitchy and randomly pushes tweets from your timeline that aren't directed at you. It's not horribly intrusive as I've probably only had at most 5 in a day get through, but it needs to be fixed.
IM+ is very well designed. Although the implemenation of Twitter push is not perfect, it's a decent first attempt and I trust it will only get better with updates. The advantage of using IM+ is that you can use twitter, hold multiple IM conversations, and browse the web all within one application. At $9.99, IM+ is not cheap, but competive with Beejive. Version 3.2 has been submitted and is in review with Apple, so SHAPE Services has decided to lower the price to $4.99 until release; so if IM+ is something you're interested in, snatch it up quick and let us know what you think!
IM+ is available for $4.99 from the iTunes App Store.