If anyone takes the trouble to read the financial press they will be aware that the Euro concept has been under strain between its members for at least two years. Until the various countries are working to a similar economic pattern there will always be a problem as some countries need to put interest rates up to combat inflationary pressures while others want to put theirs down because of flagging productivity etc but they are all stuck with the same interest rate over which they have no control.
Right now there is a belief that the Euro zone will be under a serious threat of falling apart over the next few years because of this problem. Compare the situation in Italy, Spain, Ireland and Germany just for starters and the problem becomes obviooux. At least UK has been able to take unulateral action on interest rates to attempt to combat its problems. Give the situation a few hundred years for the countries economies, working practices and attitudes to come together and the Euro begins to make sense.
Until then, keep the UK independent of the Euro. The occasional hiccup on currency excahnge for the once or twice a year traveller is a price well worth paying