Depends upon what you think of as a "recruitment tool" - and I'm going to bet that it varies both by industry and by region. Certainly different cultures (be they national or interest/skill/job related) use social media very differently. For example, the performing artists I know do far more networking, job procurement and personal-marketing on Facebook than on Linked In, but the technical folks I know center their career networking around LinkedIn.
I'll caveat that most of my experience is US based, with a significant group of contacts in India (but not the majority).
Speaking more centrally about LinkedIn features, here's what I see:
Recruiters - recruiters in the US are certainly out and about on Linked In. There's been a general model for many years of recruiters connecting to potential job seekers - I believe their goal is largely to market themselves as well connected. I found, personally, very little value to this. I got no news or information and no additional job opportunities for this connection. I expect this is in transition, and recruiters will either phase out this type of activity as useless, or Linked In will adapt in some way.
Job opportunities - there is a whole section fo LinkedIn offering job opportunities and making it possible for opportunity providers to seek out candidates. I suspect this is still quite variable by region and industry. In any venue like this, I've noticed that seems to follow a pattern of (1) not enough critical mass for anyone to benefit (2) enough job seekers and opportunity providers of compatible types are present and they get benefit (3) other entities hear of it, and the benefit provided gets lost in the noise. In essence, my take is cynical - online, social media guided job seeking still needs to find a way to remain useful and relevant and high quality when it hits high volume. I suspect Linked in varies from region to region here in where it is in steps 1-2-3
A real value - connecting - the biggest power I see to the features on Linked In is the ability to assist in forging and maintaining connections. Most forms of knowledge work involve qualifications that include - knowing your trade well, and being able to do it productively and efficiently with others in a common corporate culture. There's no real way to vet these aspects on a paper resume if you don't have a shared connection. Linked in provides a certain depth that improves job hunting. It's a two way street - job seekers can see if anyone they know works in the potential employer, and interviewers can see if job seekers are connected to a common contact. This is a great way to get more insight in the job matchmaking process, and I think at this point there's enough large scale adoption for Linked In to have a positive impact on most industries that also allow for heavy computer use on the job.
a secondary value - the messaging aspects of Linked In - at this point, many people are changing jobs, emails, cell phones, etc. quickly enough that keeping in contact is challenging. I've seen that Linked provides transitioning people with a consistent way to keep in touch. Normally I scoff at social media messaging, because it scatters communication threads across interfaces, but in this case, IMO, it usually means that job-related communication bounces up to the top since it seems to center communication around a common purpose.
There's a lot of other features on the site - groups, status updates, etc. - but I'd venture a guess that they don't have a large scale adoption.
My thesis right now is that the power of Linked in is the power of connectivity. Many people describe their most successful job placements as being based upon their connections as much as their resumes. I think LinkedIn, across the board, makes these connections easier and more reliable, and less happenstance that a pre-LinkedIn world.
That's were a I see a growing and/or univeral value.
That said - Linked In is like any other shared communication (telephones, fax machines, etc) - it's only useful if the people you try to communicate with are there too. If you find that in all the companies you've worked, only a handful of people are on Linked In, you may find that it's not nearly as valuable as I'm describing here.