I have used this implementation in three different places:
The last example raises an important integration issue, as it also incorporates Twitter Connect. People who connect to the site using one Twitter account may later on login to Twitter with another account. If you give Twitter-connected visitors these special Intent links, they may well find themselves favoriting or retweeting using the wrong Twitter account! Of course, this is only a problem for people who have multiple Twitter personas - but these people may be more numerous than you'd imagine. The safest thing for your Twitter-connected visitor is to use the regular oAuth API, but only for them.
Twitter hopes that this will be a win-win integration, since:
Overall, as a website owner you should have no qualms about using this system. Just be careful if you also use Twitter oAuth!