Some of the biggest challenges for IT pros these days include identity management, single sign-on, and Windows and Linux interoperability. A heterogeneous network presents a lot of challenges, but few are insurmountable, especially if you get some good advice. Remember the adage, "Smart people learn from their own mistakes, geniuses learn from the mistakes of others"? That certainly applies to the realm of IT adminstration.
Check out the TechX World roadshow - you'll undoubtedly gain some valuable insight. There will be tracks covering the challenges I mentioned, plus there will be tracks on virtualization. You should check those out along with the others particularly since virtualization can be a big help in both keeping systems secure and recovering from all sorts of problems quickly.
TechX World takes place in Washington DC on October 24, Chicago on October 26, Dallas on October 31, and San Francisco on November 2. Check it out!