Both times we've rented overseas has been in France. It's been mostly fun. We need an automatic, so first time we ended up with a VW Touran (small SUV) and last year a Citroen Cactus - I guess a midsize (smaller than the Ford Escape we drive, but not much).
Our only few issues was a bus almost running us off the road (the back wheel went over the little curb towards a ditch but we didn't get stuck), impatient drivers tailgating and unfortunately - putting a big scratch on an otherwise brand new Citroen with only 10,000 kms while trying to negotiate a very tight corner in a parking garage. We were covered by AMEX as we used our Amex card to pay for the rental. It took a while to get refunded and I won't go into the long story - bottom line - use the credit card of the principle driver to do ALL the booking...I used MY cc to do the initial booking with AutoEurope (since I do all the planning and booking) and even tho my husband and I are on the same account (diff card numbers) it almost disqualified us from getting reimbursed (no small amnt - $600) as you are supposed to use the cc of the primary driver. Make sure you read the small print - or even call your cc company - if you plan on rejecting the coverage offered by the rental place and relying on your cc coverage.
So go with the smallest car for your needs. Check out the fine print on the insurance. Otherwise, we quite enjoyed the freedom offered to us by not having to rely on busses and trains, travelling at our own pace, travelling to more off the beaten path spots. Don't get me wrong, we still love the train system in Europe, but sometimes a car is better. I would also make sure to check if your accoms have free parking (if you are worried about paying for overnight parking).