Bells & Whistles isn't a bad starting place (as my post says, it's the default) and it can create conversions (even the majority), but it can also be a mixed bag of candy with an ROI that's hard to establish because it's simply a bucket that all new features go into.
Compare that to designing a premium offering that a free user can hire to a valuable job you've identified among your user base. Achieving that requires more segmentation and discipline than power user potpourri, but it also commands higher prices.
Obviously I don't know your startup or how you're implementing freemium, so don't take any of the above as a judgement of the way you're doing it. This is just what I've commonly seen.
Compare that to designing a premium offering that a free user can hire to a valuable job you've identified among your user base. Achieving that requires more segmentation and discipline than power user potpourri, but it also commands higher prices.
Obviously I don't know your startup or how you're implementing freemium, so don't take any of the above as a judgement of the way you're doing it. This is just what I've commonly seen.