I actually have a Basecamp account but don't use it often. I'm a big fan of self-hosted solutions personally which is why I was excited to find your plugin.
I liked CollabPress while it was an actively developed plugin. It seems like it's dead in the water now though.
In terms of Project Manager vs. CollabPress, I think when you get under the hood, they have pretty similar features just different layouts (PM has that very easy to use Basecamp style).
The thing I did like about CollabPress right off the bat was the dashboard. I really liked how they had a central dashboard where a user could see meta's for "Recent Activities", "Calendar", "Projects", "Users", "Overview" as well as Add a Project right on that one central page. Project Manager does this too in it's own different style. For me, Project Manager Dashboard feels a bit bare; but I only have 1 or 2 test Projects so as it fills up it might not be so bad.
I do like that you can attach files to projects in CollabPress. As far as I can tell in Project Manager it only allows you to attach your files to comments in a project. My suggestion here would be to allow "add files" option under the Files tab, where a user can add a file to a project in addition to listing any files added via comments.
The Calendar View that Collabpress has is also a very handy visual tool. I don't think I saw anything like this in Project Manager.
One other thing that I like in CollabPress is that if you select a User (from the Users meta) it loads an activity page based on just that users activities; this makes for quick activity filtering. In Project Manager, no matter what user you click on in a project, it loads the project activities from all users.
In Project Manager, once you select a project there is a small "Project Info" section in the upper right. I almost always miss looking at it. One thing I have noticed is that other plugins yellow nag notifications overlap it which makes me look over at it. Maybe if you put a yellow nag like box around the items under "Project Info" it would call more attention to the items listed there.
Once I get into Project Manager (aside from the main dashboard) I like the feel of Project Manager better. I like that you used tabs inside a project vs. the meta box style in CollabPress. I like the layout of content displayed under those tabs as well. Everything seems to flow much smoother and is very straightforward and easy to use.
From all that I have seen and tested so far, I would recommend Project Manager at this point to others looking for self hosted project management solution.
If you ever choose to make a Premium version of your plugin or, premium additions to your plugin, I'd be on board with that, as long as it stayed active. :)
Things I would love to see Project Manager do (features in the future):
- Project Activities/Comments etc. not show up in the main Activities Meta on the WP Dashboard
- Allow files to be uploaded to a project instead of just to comments etc. inside a project.
- List only specific user's project activities, not all project activities, when clicking on a user assigned to a project.
- Calendar View
- Allow a secure link that can be sent to the client to give them access (upon login or by password) to specific project files (this isn't in CollabPress either)