Good game play but poor engine optimization With a big city with population over 50k, even the best video cards struggle

User Rating: 6.5 | Cities XL 2011 PC
Good game, beautiful graphics, but poor engine optimization when cities grow. At the start of the city I had all settings to high including 8x AA @1680x1050 and had ~50FPS but when the city grew to ~60k in population I had ~10 FPS with AA disabled. What will happen when I reach 200k or even 1M in population?
I wish there was an option for upgrade streets if there was space for them and not needing to destroy and then build.
Another bad thing is with the bus lines, there should be a simple add button to the current station to add a new route.
A good thing is trading with other cities it helps with the cash. It is better to concentrate on producing one or two goods for export.
When the city is small you can manage the cash-flow very easy, but when the demands for more utilities that cost a lot of money it's a little bit harder to keep on the + side with the money.