I've been quite surprised to learn that Seesmic Desktop will eventually replace Twhirl. I have tried Seemic Desktop several days, I won't say that it's a "bad" software (because it is not and it's still a "pre-version") but it definitely does not meet my needs, as well as average Twhirl's users (well...I guess so !). In my opinion, I don't see any problems with an "enhanced" version of Twhirl, but why discontinue the original version ?

What we (I) love on Twhirl is the overall simplicity (although I'm a Twitteradict, I don't need all the à la Tweetdeck options), its small window/column size (very important for Laptop users, Seesmic Desktop takes half of my 15' screen...) and its flashy (or not) color. But nevermind, I'll still keep an eye on Seesmic Desktop, first because it can only get better and better, second because I know that Loic is very careful to feedback given on its products/services.