First, let me say that I don't feel that Twitter is a panacea. However, what it does it does very well (that is when it works at all).
Let me further say that Pownce, Jaiku and the new Plurk may all be good choices for you. I have stuck with Twitter because of the way that I use it, and because there is a critical mass on that service. A few days ago, Kare Anderson asked me to share some of my Twitter "tips." Since I think that Twitter is most useful as a quick source of information, here are three that I think are most useful.
Twitter reminds me of the water cooler, where you can stand with your colleagues and banter. I use it mostly like a river of news. I hear what is said for the short bursts in which it gets my attention and often follow links that seem interesting. Some people are masters at the watercooler, but others like to get a little drink and move on.
Unruly Focus Group
You can use Twitter to mine information. Do you need to find a technology solution for a work problem? Do you need some ideas for your next post? Do you want spontaneous feedback about something? Twitter is a good place to ask. But be prepared to ask a few times over the course of the day to get a representative sample and to ensure more interesting responses. Also, be prepared to get some unusable and pithy responses, it is par for the course.
Events for Attendees, Speakers and Organizers
Twitter seems to really shine at events. It's amazing popularity really started at SxSW in 2007. It was there that the bleeding-edge early adopters started to use Twitter as a way to manage communicating at what is a truly mammoth conference. Of course, that is also a drawback for the beleaguered Twitter, which is a victim of its own popularity.
As an attendee, you can use it to find friends, listen in on some of the highlights of other sessions, have a backchannel conversation about the current session you are in, and plan evening events.
As a speaker, I usually keep an eye on my Twitter feed during presentations. Especially in a tech heavy audience, the group will often lob complaints there that they won't say out loud. By watching one can address them immediately, on the spot.
As a conference organizer you can urge Twitterers to "tag" all of their posts with a particular code #PRSA, etc. The organizer could also start an event specific Twitter account to give updates and important information and invite all of the attendees to follow it. The conference organizer could in turn follow everyone that follows them and keep tabs on the overall feeling about sessions and the conference by reading those Tweets. If something goes very wrong, they will probably find out about it on Twitter first.
Where Twitter Fails
What it doesn't do very well is foster any kind of real conversation. By its very nature it is only skin deep. Now, some people have catapulted those quick conversations into real offline friendships and alliances, so don't start throwing stones at me. However, over all as your followers and those you follow grow, it gets harder to connect.
I have a policy of only adding people who talk to me directly (@kamichat). I don't add everyone who adds me. Some people have a policy of adding everyone and some have multiple accounts for different purposes.