I used to use Eudora and Act! on Windows 2000, but I recently switched to using Eudora and Now Contact & Now Up-to-Date.
Writing this while playing with the hosted demo.
1. Contact. No place (that I can see) to put the person's photo. This is one of the features in Now Contact that I really like.
2. Contact. When I entered the contact's state it did not automatically complete it. Same with country. I like autocompletion.
3. Contact. I don't see a way to add my own custom fields.
4. Contact. One of the fields in Act! is the date you created the contact. I don't see that here.
5. Contact. Tried to create a new tag and it blew up in my face.
7. Calendar. I see how to create appointments, but I don't see any way to create To-Dos. Act! is real good at this.