A few "quirks" - technically correct behavior that still has you wondering what is going on:
- Weapon Focus is its own subtab in the feats. Makes sense in hindsight, but boy, was I searching.
- The builder associates feat slot and levels, so if you are still on your first feats, you don't get Paragon Options, even if you make a 18th level character. You can still later retrain these feats later if you need to. It also seems to keep track of your ability scores over your levels, so if you only qualified for Plate Armor Proficiency at 8th level (to get your Con to 15), you cannot select the feat earlier.
This can be a little confusing at first, but it makes absolutely sense, since it enforces "legal" characters.
- Retraining by picking Multiclass feats is done in the Powers Section, as is picking the right feat.
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I noticed a few errors:
- I recreated my Dragonborn Warlord. It wouldn't show me his Paragon Path "Sword Marshall". Apparently I don't qualify for it due to the lack of "Heavy Blade Proficiency", even though I have not only military weapon proficiency but also Weapon Proficiency (Bastard Sword). But if you use the House Rule button, you can also show "illegal" stuff and I got my Paragon Path that way.

The ways prerequisites are checked might need to be tested more.
- There are some spelling errors. Catsclaws comment might indicate that this could be a problem if it is supposed to be a keyword/rules term like an ability score.
- There are still some powers that are not correctly formatted on the Character Sheet, for example Dragon Breath. I think that's my biggest gripe, since it makes the sheet less useful.
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Something I miss:
- A way to remove the item power cards only from the sheet. I need a shorter description or something, because I don't want to print 6 pages just for a few item powers!
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I suppose I should compile my list and send it to Customer Support or their Error Reporting.
Overall, it's fun. I think I will spend a lot of time these weeks to test-drive the app and create more PCs.
2Oldtimer: Could you figure out what they are using to create the MSI Files? I wonder if that tool is flawed...