You can have multiple tabs open with several advanced searches going on. This seems like an improvement over something like Twitterfall, which is browser based, and doesn’t have the same advanced search functions.

Here are Yahoo’s goals for the app:

• Create a desktop application that allows for the creation, grouping, and auto-execution of advanced search queries against Twitter
• Leverage existing skill-sets and tools
• Target the Windows, Mac OS X, and Linux operating systems and minimize the amount of platform specific code that must be written
• Open source the code so that others can learn from, contribute to, and/or extend the product as they see fit

But to be fair, it does also seem like the ONLY advantage is the advanced search. Sideline offers very little in terms of interaction, you can’t reply or DM anyone, you can’t even log in. You can mark tweets as favourites, but as you are not logged in, these will only be saved locally and won’t be viewable in your Twitter favourites.

Except for being a desktop client and featuring tabs, it doesn’t offer much more than the official twitter search. It only updates every minute, you can set this to be less frequent. But you can’t have it update every two seconds or so, meaning if you monitor popular search terms, you will be bombareded with 100’s of results to go through every minute.

Hopefully Yahoo will improve this Twitter client in the future to include some of the features that you have in TweetDeck and Twitterfall, but at the moment it doesn’t seem very usefull. I will stick to Twiterfall for my Twitter searches. But as mentioned on mashable:

Sideline seems to be more of a research project for Yahoo rather than building a new major new product or division.

There hasn’t been many reactions as of yet in the blogosphere, but there has been a few on Twitter:

mahadewa@avianto That’s cool :) re:sideline 2 minutes ago from TweetDeck in reply to avianto

alicam: Not sure if we need another Twitter search app but it works nicely – http://sideline.yahoo.com/ 2 minutes ago from TweetDeck

frumpa: trying out Yahoo’s Sideline but the links are NOT active hyperlinks http://sideline.yahoo.com 38 minutes ago from TweetDeck

e_D_D_y: Is Yahoo! SideLine an April Fools joke ? Can’t get any result, it’s just… empty :( about 1 hour ago from DestroyTwitter