To be honest followings are not actually Cons for me:
1. In time of work you can get a homely feel, no dress code, no extra burden to carry your ID Card, no burden to wear formal dress in rainy season. So, you may say, they are not professional.
Though, I do not think so. If a company handling 100's of Customer daily without any subordage, they can't be unprofessional.
According to me, instead of saying them unprofessional you can maintain your formality, no one will stop you :)
2. They have a good amount of work pressure. Bro, this is not a Govt. Organization, if you want to learn something you should need to have a willingness to take work load.