Anyone Worked With a Mobile App Development Company in the USA?

[jameswillreal]

I’m doing research for an upcoming project and trying to find a reliable Mobile App Development Company USA. Before I commit to any team, I want to understand what it’s like working with different companies.
If you’ve worked with a US app development company, could you share your experience? I’d love to know things like:

• How they handled complex features
  
• Whether their customer support was responsive
  
• What the testing and launch process was like
  
• If they offered ongoing maintenance
  

Any honest feedback will help me make a better decision.