I may be missing out on possible links but I pretty much ignore any of Ancestry's 'suggestions' other than the 'common ancestors' one. As you say, the others seem to be full of other people's errors. Its quite soul destroying when you 'review' trees of others with a similar name as yours and notice that one of them has made an error and all the others have merely jumped on the bandwagon. Why do these people bother of they're not prepared to do things properly? I have picked up on info that I hadn't known, but I always try to check it out for myself before running with it.
Also, I do find searching for matches by surnames every few months often comes up with new info.
But, oh how I wish people would include a tree when they do a DNA test. I'm not asking for one of those with 10,000+ names - often just a few generations will do. Sometimes, you can work with one or two surnames and placenames.
I appreciate Ancestry can't strong-arm people into including a tree but surely they could require people, when registering, to say where they're from and what age range they fall into. At the moment this info is only requested and, most of the time, not completed. More than once, I've managed to find someone's link to me through their surname (assuming its not Brown or Smith!) and their location, mostly by using FreeBMD to start with.
Perhaps Ancestry would consider requiring people to fill out their personal data rather than just requesting? Its not as if its overly intrusive.