I just received an invitation to test out the new Garmin Connect "Modern" site today. Some of the new features are pretty cool, my favorite that clicking on the logo in the upper left brings you back to the main dashboard page. The dashboard looks really sharp, even though I can't get certain features to work. (I can't add the courses module, and the Personal Records one just shows a picture of a trophy without any data). However, this UI isn't carried through to the other pages of the site. I'll walk though the ones I use on a regular basis and describe what I think could be changed to make the UI look better.
Activities: The search box at the top looks nice, however when you open up the filters, it just seems like there it too much white. The filter categories just blend in with the background. There should also be some kind of separation between the search field and the activity window, and if the search box was moved upwards a little, there would be even more room to show activities. The "Buttons" to edit/delete activities are terrible. A blue bar with white text like on the dashboard would look much better, preferably with a bit more padding on the left side. Also, the activity window is designed poorly. There are 2 different scrolling sections which is very confusing especially on smaller monitors. In fact, when the window is small, the export to CSV button is missing at the bottom, and not even scrolling will reveal it.
Activity Page: Everything seems to just run together, especially with all the buttons/hyperlinks at the top of the page. When viewing another user's activity, there is a random blue circle around the Elevation Corrections text. The scaling is terrible. On a large monitor, there is too much whitespace on either side. However, when the window is small, there are 2 scroll bars and the content does not fit in view. The new player is also missing a full screen option.
Calendar: This seems much better to me than the activities. One thing that could be improved is the "collapse" button for the left sidebar. The cursor that appears makes the user think that they can resize it, but instead the sidebar just disappears. The calendar UI appears to be the same as the old one (instead of the new modern UI), but I think it still looks alright, and I'm sure it will eventually be updated.
Connections: I really don't use this page much, but I noticed that there is a TON of white space. The left column should resize dynamically with the size of the browser window. On a large screen, the Map could be extended on the Activity feed, and multiple people could be displayed per row on the My Connections and Find People Tab. As with Activities, when using a small browser window, some of the content is hidden. For example, the leaderboard runs into the boarder on the right, and the left column is hidden by the navigation bar.
Courses: Appears to be just copied from the old UI again. The map section could be extended down about another 3 inches on my monitor, and the course list is even shorter than that. Increasing the map size would make editing much faster. Also, not really a UI thing, but when clicking on create course, the map should move to the location the user was previously viewing, not the area where they live.
Reports: As with most of the other pages, the content should be able to dynamically resize depending on the size of the browser window. I think it would be better to see a little better separation between the sidebar and the graph (as in like a visible divider). I also miss the ability to get reports for specific time periods, this should be added and the scales should be modified accordingly. And when clicking on a specific activity (when viewing average pace for example), that activity should open instead of only showing the date.
Overall Feedback: I realize that this modern site is a work in progress. I just want to share my thoughts on what could be improved. My biggest concerns are content scaling depending on window size, and the look/separation of the new button/list styles. I'm by no means a UI designer, and these are just my opinions to make the site look even better.