I use Seesmic on my Droid for twitter. I can set intervals in the settings for polling as little as 5 minutes, I believe. I can also have it send me notifications of new tweets. I follow a ton of people, so I turned this off... else I'd be getting notified every 30 minutes when I'm scheduled to pull. I only get notifications of DMs or Replies.
Thats the thing. When you go to twitter.com you can choose whose tweets you want to recieve. There is this small phone icon next to their name and you click it and it turns green.
This way you dont recieve everyones new tweet....rather just the people u choose to recieve it from. You cant do that thru an app...only thru online which is what I've been saying here.
and it seems like at times theres a delay of when u recieve those tweets.