I have been reviewing LINQ since last year, but I had never had a chance to actually jump and use it extensively. My last project uses Visual Studio 2008, and there are opportunities to use LINQ.
Probably because I have reviewed it before, the learning curve was not that steep. I use LINQ to SQL and LINQ to XML, and I love it. Prior to use LINQ, I had to open my XPath reference book when I was dealing with XML and XSLT. Now, I don't really have to deal with the plumbing, and let LINQ does it for me. It increases my productivity. Troubleshooting is much more straightforward.
LINQ to XML does not replace the flexibility of XPATH and XSLT. I still like the level of control and flexibility that XSLT and XPATH provides, but for most of the time, LINQ to XML serves my need.
So, if you are using Visual Studio 2008, I encourage you to check it out.