i too have been having issues with this on my 9700. However i also have an android 2.2 based phone and it works flawlessly over 3g. Also both phones are on the same carrier. Too me this sounds like an application issue and not a phone/carrier issue.
just installed AppWorld and this App. Looks almost the same like the android app. Problem here is, that all settings (like filters) are gone if I close the app and fire it up again. Also I'd really love to see that a "message" pops up like in the web interface of Sysaid when a new message arrives.
The controls aren't that intuitive as the webinterface is. Handling seems a bit bulky.