I am all for the Nationwide card, since you will get almost the market rate on the day you use it - great if you are there now, and getting up to 1.98 which is the highest the rate has been for a decade or so. The big disadvantage is that you can't tie in that rate for travel later in the year - the only way of doing that is to buy currency now.
2 years ago we were getting 1.91 to the £ in NY in February with the Nationwide card, but by November when we went to Florida, the exchange rate was around 1.75, and I wished we had bought out currency earlier.
It's impossible to predict what the rate will be in 9 months from now - but if you can tie it in at over 1.90 by getting currency now, I think you are getting a v good deal.