I've never had issues with this add-on myself (been using it on Chrome & Firefox for 4 years), but I do wish the developers were a bit more active and listened to user feedback. There are a lot of small features that could be added, which would improve the usability greatly. Secondly, I wish there was a way to sync the tabs across browsers (e.g. via your GitHub account and Gists or via Google Drive, Dropbox, whatnot) instead of having to export/import manually..

Other than that, I love the simplicity and it's one of the first add-ons I install!