What is the downside of using GO SMS Pro and / or Handcent? All I've been seeing about these apps are the positives. I want to know the negatives of using them, apart from me having to install an additional app to do something that the phone can already do by default. I'm looking to using one of the two because of the built in support for backing up SMS and MMS, something that will come in very handy especially since I text often.
I can only comment on  GoSMS which, while being a great app, has a few obvious issues.


Texting via GoChat is, at best, unreliable. With both parties connected to hi-speed broadband, texts take their own sweet time to deliver. These texts shouldn't expire but they do. Given a certain amount of time, texts stay undelivered.
If you have root access and are thinking of uninstalling the stock SMS app (which would be the logical thing to do), bear in mind that GoSMS notifications don't work hand in hand with the app's UI. Meaning, if you see a notification in the status bar and press on it, it will lead you to the main app interface but you may or may not see the actual message. This happens often when you receive more than one or two texts at the same time. Strangely, even though you can't read the texts (I assumed they were lost), you will have an irritating notification indicating that you have unread texts (that you obviously can't read because they don't show up). Having the stock app ensures that GoSMS shows all texts, unread or otherwise. Also, when you have read the text in the stock app, the notification from GoSMS disappears.
Local backup only works when you aren't connected, either via Wi-fi or mobile data. With the latest version of the app, everything gets backed up to GoCloud. This happens only if you have signed up with GoChat.


Hope this helps.