Twitter has it's uses, they're just not many and the way the service works is too restrictive.
Being able to receive all twits on certain hashtags is something I'm surprised it doesn't do.
Likewise being able to filter out hashtags from people you otherwise want to follow would be nice. I don't care about the darts, thank you Stephen Fry.

Were those added, especially the first, it would be a far more powerful platform. As it stands these are only possible with custom twit clients, many of which are fundamentally broken in other ways, try to do too much of everything (i.e. other social networks as well) or run very slow. Often all 3.

So, it's an amusement I use on my phone mostly. I got involved in some of the UK election stuff on there, but otherwise I'm a twit very rarely. Sometimes do updates on my game dev stuff... That's pretty much it.