I've been on Twitter for going on nine months now, and, for the most part, it's been a surprisingly pleasant experience. I've met some great folks, including fellow readers and writers. One good aspect I've noticed on twitter is just about everybody tries to "play nice." The few that don't, I guess, end up getting blocked or unfollowed. Which brings me to my next point.
Creating consistently interesting and worthwhile content for tweets takes some effort. At least it does for me. Variety is what I strive for, rather than repeating the same "buy my book, buy my book" pitch. I read a "20-1 Rule" where you post 20 tweets (not counting retweets or RTs) for each book tweet you make. It's better to give than receive.
Of course you get out of what you put into something. The time invested in twitter can't be evaluated in terms of what returns you get from it. I like to practice time management while using twitter, so I don't let the time get away from me. The twitter admins also impose a ratio rule of followers v. following on its users. That means if you're inactive on twitter, you're likely to lose your followers. So hey, if you're ever on twitter, drop me a tweet.
I'm at @edlynskey.
Ask the Dice
(Newest Stand Alone Washington, D.C. Crime Noir)
The Zinc Zoo
(Newest P.I. Frank Johnson Mystery)
(likewise it's been a pleasure making your aquaintenance on twitter this past year)