It was fairly satisfactory.

The attendant at the key pickup location was a bit impatient, which wasn't a great experience. Fortunately, at the car pickup location, the staff were very patient and friendly when answering questions. Much appreciated!

Staff will usually recommend you buy full insurance; it's a good way for them to earn money. It's up to you, of course. Full insurance provides safety in case of accidents, but for ten days it depends on your driving skills and your knowledge of the routes, rules, and your destinations. I didn't buy full insurance, just the standard one. The staff was helpless but said the compensation in case of an accident would be very different. I firmly refused.

Detailed explanations

Managed to get a free upgrade from our booking. Excellent customer service. Service staff re-iterated requirement to get vignette for driving into Austria.

Did not check if there's any price drops from my booking date. Otherwise, seamless experience.