The value of bots on the forums worth having links on is rapidly decreasing because detection is improving. The serious downside of using xrumer (or anything similar) is finding yourself banned from the forums that really count... and even if you return with a new ID and hand-built posts you may get canned the moment they see a sig that spammed the heck out of the forum before.
OTOH, if you want short term gains and a bad rep longterm... the method works fine.
To many "good" sites are getting far to wised up for general spam now, and as you say, it can have a major knock on, in the sense that it can lead to a massive loss of rep, and the removal of legitimate links.
I know a few forums now that stick any spammed link into the word filter, so that if people come back, and add a link legitimately by hand, they get to post nothing more than http://************.com, and that sort of thing is only going to increase.
It's like a lot of things, the amateurs who don't know what they are doing, help kill it for those who do.
XR, and other such tools can still be useful, but I'd say, personal experience, tells me that only about 1% of people can use the thing effectively, and most of the other 99% just make things worse for that 1% every day, that's especially true if you're working on a "quality" project, rather than something that's short term, and that it doesn't matter if it get's slammed as spam.
It really does depend on how you do it... i've been "using" a very dear list of mine for some time now, and occasionally when I check a forum, some guy called XxaxljsxjaxASXa creates a thread, and there's like 100 posts from him there...
Sure the IP is different (proxies) but the rookies use the same name... and the "advanced" ones use generics but it still screams "FAKE" and the post is the same...
Some people have no clue, it really is so obvious, and screams "I am a spambot!" and then it becomes counterproductive, not only for the individual, but for everyone else too, as it leads to forums upping their filters, and controls.
In my opinion, there's nothing called a "crappy" link ... it all adds value, just some more than others..
Technically that can be argued, but then you can also give someone a skateboard, and argue there's no such thing as a crappy car, but I doubt the guy who wanted a "real" car would be happy that he got a skateboard instead.
The value of a "crappy" link can be so low that it's not worth any time, effort, or finance to achieve, especially if it shitcan's your reputation.
I've watched people go out before and get 200k "crappy" links, and rank lower in the major search engines than people with about 2k regular links.
Am I going to spend time, money, and my reputation to do it the first way?
No, so to me it has no value.