Perhaps, but they seem to be more up to date than the maps I bought from Garmin for my hiking GPS a few years ago. I bought the 2008 version of their 100k maps for the U.S., and found that Lake Nockamixon (1,450 acres) and Marsh Creek Reservoir (535 acres) were both shown as the tiny creeks that were present before they were dammed up to create the lakes in 1974 and 1973 respectively. Imagine that you are hiking along and encounter a lake that is a few miles long that is not supposed to be there. Those lakes are showing up just fine on the USGS site.
When I complained to Garmin, their response was that it was not an error and I should buy the (more expensive) 24k maps, which do show the lakes. They claimed the 100k maps don't have enough "detail" to show the lakes, yet they do show the tiny little creeks that were there 40 years ago, and they show other lakes that are only 22 acres. So, Garmin will happily sell you maps based on 40-year-old data and then charge you more to upgrade to newer data. By comparison, the USGS maps seem stunningly timely.
OpenStreetMap often lacks detail in the U.S. (it wouldn't be surprising for an area to have missing water bodies...), but maybe you are in an area where it is useful.
For what it's worth, the gtopo 24k product is pretty fantastic. Recently used the heck out of it on a 10 day hunting trip, it had a pretty ridiculous amount of roads not shown on any other detailed map.
One downside though is they are obviously using some elevation and image analysis to auto detect drainages and mark them as water. A significant number of draws in our area were marked as creeks, when it was actually an ATV trail along the bottom.
Other than that, a very very worthwhile product if you plan on doing any serious hiking/motorcycling/etc and plan on extensive use of GPS.
When I complained to Garmin, their response was that it was not an error and I should buy the (more expensive) 24k maps, which do show the lakes. They claimed the 100k maps don't have enough "detail" to show the lakes, yet they do show the tiny little creeks that were there 40 years ago, and they show other lakes that are only 22 acres. So, Garmin will happily sell you maps based on 40-year-old data and then charge you more to upgrade to newer data. By comparison, the USGS maps seem stunningly timely.