We had the following experience:
Our company has many departments which are distributed inside and outside the country (3 countries to be clear). The number of users is about 110. We have used the File Mode, then the SQL-based Client/server mode with separate infobases and nowadays we have an integrated single infobase in Client/server mode. Here are my recommendations:
1. There is no doubt that the database should be kept on a separate SQL server (we use MS SQL 2008 R2 on a server with 48 GB RAM and 8 processors);
2. 1C:Enterprise server is installed on a separate server. There are 3-4 work processes (for each group of 40-50 users a separate work process is used);
3. For each group of 40-45 users a separate terminal server is used (with 64 GB of RAM), we use servers with MS Windows Server 2008 R2 since it's much more stable when many users are working through the terminal compared to previous Windows Server releases;
4. Optimize the Print Service on the terminal server to limit the number of printer models and drivers and leave only network ones;
5. Between servers which handle your infobases the connection should be wide and stable. For your number of users it should be about 1GBit/s. It could be achieved if all servers will be on a single switch (in one server room) and not distributed around the country. Our company leases servers from one of ISP because to own servers is not optimal for us, but it is disputable;
6. For this number of users I recommend you to have a really experienced 1C administrator. The one who will monitor and resolve conflicts in 1C and help programmers to find bottle necks in configurations. Trust me, this person is “must have”;
7. About the question “use a single infobase or several?” it is a question of methodology. There is a main person in your company who is interested in receiving the consolidated reports for entire the company and does not want to perform consolidation of Excel books from different departments, if your organization has an accounting methodology department, if your management is ready to invest in reliability… In that case I recommend combining all your organizations in a single infobase.
Hope, my advice will be helpful for you.