For Twitter there is also at least TweeGo and witter (not a Twitter user myself so can't give any more information about these).For youtube there are many options, Mediabox and @scene to name a few. For navigation I would suugest to buy Sygic Mobile Maps, 100x better than the default Ovi Maps.I myself don't have use for task manager wery often, but if something seems to be slowing down your phone write "top" to X Terminal and then if some program is using too much resources kill it with "kill" command.For IM's the default Conversations is pretty god IMO. Additionaly I would suggest you to install this and swapolube to make the user interface a bit more fluent. And for the email client search the forums for "modest fixes". Also searching this thread is a good way to get known to good applications. Be aware that many of the applications I was speaking about are from Extras Devel, read about it from the Maemo Wiki before enabling it.