Once you have 50 million resources, 10000 max population, and nearly 8000 units on the screen at a time, it begins to lag WAY too much. It's so fun though...
Got to floor 20 and then died. Not a single achievement was given. I'm not going to waste any more of my time on this game, as fun as it was while it lasted.
You may begin to notice that you can't play on the internet with a separate tab, because this game pauses when you leave the page. A way to counter this is to open up a second internet browser and continue doing whatever you want to do on the other browser.
A way to spend stats faster would be a nice addition. I hate it when I'm trying to respec near the end of the game and I have to spam my mouse button millions of times to spend my points. A system like the Marketplace's stone buying/selling system would be nice for stat spending.