Feature of EC2 is that the other Amazon services such as S3, SimpleDB, Simple Queue, etc. will work faster. If you store data in the SDB, the files in S3, messages in SQS, then give/receive their best with the EC2 instance, because scaroth data exchange within an infrastructure Amazon is very high.
In General, EC2 is expensive, and its instances are not protected from falls. Thus irretrievably lost ALL data. Therefore, the use of EC2 add service use the virtual drive (mount), which will always be a backup on S3. Feel? One service leads to another. And you will have to choose whether to switch to amazonesque the cloud completely or to look for alternatives.
As has been written above, I would recommend linode.