I rooted my Milestone in 15 seconds by downloading and running Universal Androot from the Marketplace.
Haven't seen any disadvantages of doing it since then.
You can then remove any pre-installed app in a couple of easy steps.
For example, here are the step by step instructions to removing Motonav trial (which takes up lots of space btw).
You can also remove any application if you know the apk name and the package name.
For example, to remove the QuickOffice trial:
use
QuickOffice.apk in step 5, and
com.qo.android.moto in step 9.
Here is a good list of apk and package names.
Hope that helps.
