I am considering using SQL CE for multithreaded server where there is at approx. 80 clients often (secs) working with data in DB. I know MySQL (EDIT: unoffical servers) has no problems (World of Warcraft speaks for itself), but what about that? Thanks!
For a server, I would recommend SQL Server Express Edition - I have used it on a server with higher loads than you mention with no problem. Is there a reason you are using SQL CE? To my knowledge, SQL CE is recommended primarily for embedded apps and on handheld devices where you cannot use a full server-edition product.