Performance seems to be a common problem in Sage Line 50.
I think it's fair to say that some operations are slow, particularly when there are lots of transactions on the system, but equally I'm not convinced, unlike some commentators, that network configuration is not a significant factor. It's also kind of interesting to compare Sage running on an old Win98 box and an all singing and dancing XP box accessing data files on the same server.
It's quite possible that Sage haven't taken the time to test some of the issues in a controlled environment, but we have and significant performance gains are available for relatively little effort.
For example, using a unc path to the Sage data files rather than a mapped drive letter can reduce performance by 50%.
Similiarly Norton AV on the Sage dta files will grind Sage to a halt.
Turn off Opportunistic Locking on the client or server. There are lots of Microsoft Knowledge Base Articles on this subject.
There are another couple of Windows Server Policy settings that have dramatic effects on scrolling through lists of Invoices for example and the speed of reporting but I'm not going to list them here because a) We need to make a living and b) You run the risk of messing up your system if you don't know what you are doing.
You will still need to extract data for some operations because, yes, Sage uses an old architecture and some fields aren't indexed