i saw your post on pen-test and was getting around to a response, but since you posted here and i can get in more detail (aka shameless plugs).

i think you received some decent responses to your question with the exception of the jerk who told you to go play the challenges on pulltheplug.org.

while challenge servers have their place in any training program if you dont have a solid foundation in the basics or dont understand why doing a certain thing or command actual beats or completes the challenge you are lost.

I havent looked at the infosec institute materials, so i cant speak for thier quality.  what i can say, because we have worked with mentor led and self paced course at www.learnsecurityonline.com, is that most people get frustrated and quit self paced programs because there is no one to help them when they get stuck or give them encouragement and incentive to continue on. 

so i would encourage you to take a look at what learnsecurityonline.com offers:
http://learnsecurityonline.com/LSO_Programs_September2006.pdf

we believe in developing well rounded security professionals by making sure they have a strong understanding our "core competencies":
Programming
Networking
Operating Systems

that allows you to build on the "advanced competencies":
policy
auditing
certification
cryptography

if you are interested take a look at the programs and if you have questions post up.

good luck with your decision and training.

P.S. we do weekly rootwars on saturdays (open to all) so if you are interested you are more than invited next week.  we gear them to a beginner level so all skill levels are encouraged to play.

-Chris