Thank for the write up, and more importantly, the excellent suggestions.
All of the issues you have mentioned are on the roadmap (if they were not, we added them); however, those items voted by the community with get implemented first.
Now that the TechCrunch40 is over (Notifir's funder ThemBid.com was in the Demo Pit (of which I am a co-founder) we will have more time to enhance Notifir.com.
We have already implemented version one of the top voted feature, which is the submission submitter tool.
However, before going on to the next voted feature, we will work on the errors. Digg.com has gone through several changes the past few weeks that will cause us to do some further tweaking. Most of the errors occur when we have issues with communicating through the API.