+1 - I want this too.
My needs are a bit different though. I have a lot of recurring costs in USD and GBP because of different types of memberships I have. My local currency is NOK. I can't enter these memberships as scheduled monthly transactions because of changing interest rates. Doing so would screw up my numbers.
What I'd like to see, which should be *fairly* simple to implement, is support for me adding those costs in e.g. USD and on the day they are withdrawn, YNAB will do a database lookup to query the current exchange rate and convert the entered amount for me. That way, YNAB will help me keep my workload lower so that I can focus more on the actual budgeting itself.
I realize this usage scenario is a bit different and maybe even more marginal, but I think it would be a neat feature.
I feel like I shouldn't have to manually enter all recurring costs simply because they are in a different currency.