I run 2 servers right now, one at home is running 24/128 up/down, but my actually ratio is 1:1.12 (basically 24/26 so the caps don't really matter)
I set it to 24 because if I set it any higher it hits the limiter my isp put on the connection somewhere around 28. If you set your upload rate to something ridiculous like 1024, then watch the bar graph, it will jump around *a lot* but the average of that jumping around will be the maximum you can set your upload speed to - at least for that time of day.
I also run a server from... somewhere else

there I have it set at 256/512 (yes, bytes) at night, but during the day I have to lower the caps to 50/50 to make sure it doesn't use too much of the connection, funny thing about that server is that it's uploads are almost always equal or higher than the downloads - this could be because I have trouble figuring out things to download on the connection that take it more than a day, but in the end, this server ends up serving out a whole lot more than it downloads.
When setting your upload limit, just remember that in a perfectly fair world, your upload speed would be exactly your download speed, for a file sharing network to work, the same amout of information needs to be uploaded as get downloaded, actually a little bit more because of corruption.