Guys, I need your valuable product feedback.

Nice work. It seems well focused on the things I'd personally find useful - best day/time to tweet; managing followers; scheduling tweets. Also, the UI is very straightforward and easy-to-use.

Some suggestions:

1. Lose the ads. They'll earn you trickle income but completely destroy the design of the product and my faith in potentially paying for it in the future. Ads are for websites, not products like this.
2. "My Tweets" includes stuff I retweeted, so "Popular Tweets" isn't really showing anything relevant to me, just really popular tweets that I re-tweeted. An option to exclude retweeted posts would be much better.
3. One nice feature when managing followers would be to see my followers/people I follow based on how much interaction we've had together - my tweets they liked/retweeted, their tweets I liked/retweeted and so on.
4. Would be good to get the person's Twitter bio when viewing followers/people I follow - for many I'm not sure who they are just from their name/username/avatar.
5. Love the idea of best day/hour to tweet. I know you can drill to the day level on the best hour already, but would be good to see this represented on a heatmap grid to quickly see when the best day/hour combinations are. Or even if you had a tile that just tells me the best day/time to tweet overall rather than having to decipher that information from the charts.
6. Would be good to factor the best day/time feature into the scheduling feature too. When I'm scheduling a post and select a date, suggest to me what time I should post it at for best reach.
7. I can see some people being uncomfortable connecting their Twitter account before they see it in action. Might be good to do a Baremetrics-style demo at some point where people can actually use the product in read-only mode to get a flavour for how it works, before committing to connecting their account.

Good luck with it - personally I think it's something I could see myself paying a small monthly fee for (~ US$5-10) in its current form if you lose the ads.

First thing, I am interested in why you went desktop app instead of web app?

Not saying it's wrong, just interested in why. Was it due to GDPR?