Worries about the Danube Route
These were our initial worries: the trip was too easy, it was too crowded, and the scenery would be monotonously the same for the length of the river.
As it turned out, there was some small truth in each of these worries, but none was nearly as bad as we had anticipated. As for the path being easy -- there is no doubt that it is. It is advertised as completely flat, slightly downhill, and with the wind at your back as you bike east. What could be easier? However, I wouldn't say that it is completely flat. There are numerous ramps where there are short, moderately steep ramps rising 10 to 20 feet, and there are several steep climbs up to bridges. There is one day (of the six) when biking through the Wachau (wine-growing) region where the path leaves the river for moderate climbs among towns, orchards, and vineyards. But if you really want hills, take any of the recommended sightseeing excursions. If you want to visit a monastery, a castle, or a museum -- well, they are all perched high on hills overlooking the river.
As for being downhill -- the path descends a total of about 400 feet in the space of 230 miles. I'd call this flat. And I waited for the wind at my back, but for at least two of the six days that we cycled the wind was noticeably in our faces. For another three days there was seemingly no wind at all, and on one day we had a tail wind. We noticed a lot of bikers heading the opposite direction, i.e., west, but there is no doubt that most traffic does go west to east, because the tour operators truck the bikes back from Vienna to Passau.
I had read that the Danube bike path is very crowded in the summer months, and that since all riders start from the same intermediary points (the same hotels) at about the same time, there are traffic jams on the path. As it turned out, this worry was greatly exaggerated. The path was reasonably crowded, particularly near the towns on the weekends, but there were other long stretches when we wouldn't see another cyclist for perhaps ten minutes. We did get in "synch" with certain other small groups that we would encounter from time to time, but we never saw any of our own tour group after the first morning. About once an hour we would be passed, or would pass, a "peloton" of perhaps 20 to 30 cyclists, and every fifteen minutes or so a solitary biker, looking like he was doing the Tour de France, would pass us at great speed. On balance, I wouldn't have called the path particularly crowded.
As for the scenery being monotonous, I didn't find this to be the case. You can check the photos given here in the links to the descriptions of each day's travel. About half the path has a certain uniformity, where you are cycling alongside the river on a dedicated bike path. Ahead you see a castle perched on a hill on the opposite side of the river. A swan waits near the bank as you cycle by. On the opposite shore you see small, ant-like figures that are cyclists like you on the path across the river. It may have a sameness, but it also has a calming beauty.
Moreover, the path has more diversity than I had anticipated. It often departs from the river, going through small forests, farm fields, and charming little towns.
I was never bored.