We have two instances set-up for our projects, one of them is Windows Server 2012 R2 with MySQL 5.6.11 and PHP 5.6.11 installed for our web-based products, we have done so much optimisation to get the websites much faster but after fully deep monitoring, we found that our internet connection speed for the instances is two low not to mention that remote desktop connection is usually so slow. We need to have our instances internet speed much faster. This is a big problem while connecting to our databases.
Network performance of ec2 instances depend on the type. Refer to the Instance Types Matrix here: http://aws.amazon.com/ec2/instance-types/
For remote desktop you will also want low latency. Make sure you choose the AWS Region geographically closest to your users. See: http://aws.amazon.com/about-aws/global-infrastructure/