Using currency conversion in GS has been a big plus since introduced but it still has some limitations that we have to use the rules rules engine to get around. 

1. There is no support for currency conversion for a given date range. 
   Businesses need to be able to show currency more accurately for long term contracts around renewals etc and having one currency conversion in the system limits us so we cannot display the currency say for the beginning of the year vs current numbers at the same time
2. It would be great to have the currency conversion work at a record level instead of at a global level. For example, a given contract could have started 3 years ago and the currency exchange rate for that may have been way more or less at the beginning of the contract than it is now so having the value stored at the record level would allow the calculation to happen either by storing the conversion rate or a lookup to a rate card for a given time period.