There is a debate over this topic, and, I'll give you my view on it. I run Windows XP Professional as an admin all the time (even now), and I don't have problems. That's because I'm very careful about what I download and install on the Internet. However, for new users of computers, or people who aren't so wise about what they are downloading, a admin account might not always be the best thing.
Windows XP Pro has a user account feature called a "power user". It's basically a account that can do half of everything. It's somewhat in the middle of a limited and admin account. So there's no pathetic when you click on the clock "you don't have appropriate account privileges to access this function" or anything like that. It works quite well (I have set some of my family up with this type of account).
Another thing is with a power user account, you can still install programs and such, you just need to enter your admin account's password. So you still don't even need to switch user accounts!
My simple answer is no..