If you judged the popularity of a series based on how much fanservice fans create a quick look to see only a couple pages worth is a clear indicator of just how unpopular the series was. So yeah it's not a very popular series and yet I still watched it to the end. Why? Probably because it had so much potential but got trapped in the cliched duldrums of school based mecha battle blah blah blah lets toss in some romance harem stuff for good measure. However, I did love the talking rock with the visible wording and what have you. That and the battle maids for me made it worth it.
The character development was rushed or just tossed out the window occasionally. At times you were left wondering why this person was doing this and that. So it really did just become too jumbled with various characters and their role in the series. And then add to that the double end and redemption of the original bad guy you left at the end wondering exactly what the hell just happened.
You can still watch the series on Crunchyroll and hulu if you want to check it out and if you really like personal mecha suits and the whole school life thing then it shouldn't be to bad to just waste some time with it since you don't have to wait until next week to see the rest. If you want to know more about Sacred Seven I suggest reading the wiki page for it that does a better job than I would be able.
Here are a couple trailers for the series.
