Not neccesarily. I've had good luck with the smaller, privately owned Giant shops. I've received excellent service from the 3 shops I've used the most, 2 in Tainan and one here in Hsinchu. From Taipei there's plenty of good weekend rides that you can do right out of the city, or maybe get on a train to get you and your bike out of town. There's also some decent scenic rides in and around Taipei. If you haven't already, check out the cycling section on Forumosa: http://www.forumosa.com/taiwan/viewforum.php?f=134
Post what you're looking for and someone can point you in the right direction.