While studying in the app, it will now and then sound a bell and say "New word added". So far so good. However if you continue studying without returning to the home screen, I have the impression that by the time your work items get down to 0 you didn't really encounter these new words. Indeed, when returning from the home screen and starting studying again, you'll suddenly have many new words to study. Once, I hadn't gone back to the homescreen for a few days, and after continuing studying I had 35 new words....

Yes, I have noticed this too in the past few days.

Today, I had 22 characters due, I added 10 words, and still only had 22 characters due. At the home page, it says "Syncing..." and was not getting to "synced".

I had to reboot my iPad and relaunch Skritter in order for it to complete syncing and add the words.

Sounds like there are still some issues with syncing. If it doesn't say 'synced' at the end, then it probably had a problem with corruption when trying to download the data from the server. There's a system in place to make sure downloaded data that's corrupted isn't saved, but there isn't a great system for telling you when that's happening or when it pauses trying to sync due to frequent errors. I'll work on making it clearer when syncing isn't working due to iffy networking, and see if we can make it a bit more resilient.

To see if that was the case, this morning I went to the main screen, and watched the app sync. Done! Then I went into study, having about 30 items todo. When I was almost done, the app showed "new word added", but the number of workitems remained the same. Nor did I see internet activity in de left upper corner of the iPad. When I was down to 0, I returned to the main screen. The app started syncing by itself, successfully. I went back to study immediately: 25 items todo. The whole process took maybe 15 minutes and I was on my home wifi network, I'm pretty sure the comnection was allright!

I have items added, but they didn't show up so far, although I brought the items due down to zero. I can clearly see this in the list, which I am studying: the items are in grey in all 4 categories, but they never showed up. The missing items are not in a consecutive sequence, sometimes only one item in between items, which showed up, sometimes up to 5 items. The list was finished and is no longer under study. I used "fast adding".

I use the app too and I had quite a few issues with new words so far.
Since I started using it my progress plateaued because no new words are added unless I do some studying on the website too. As soon as I study three or four words on the web my items list hits 20/30 new words. Unluckily when I go back to the app the due items list seems to shrink almost immediately and I end up with just a few new words in the end.
The whole process is frustrating and the workaround hardly effective. I hope you'll be able to come up with a solution for a product which is otherwise excellent.

@tommasominnetti: What's your retention rate set to? Have you tried lowering it?

http://www.skritter.com/faq#retention

@lechuan: My retention rate target is set to 95% and the current retention rate displayed in the progress page is 96.4%

Previously I tried to lower the target rate down to 92% and even 90%, while setting the word adding speed to fast, but both settings didn't get me any new words as long as I stayed on the app. That was the reason why I went back to the website, and as soon as I did that I was flooded with new words.