Passed the IINS earlier this week... 933/1000 after 3 weeks of preparation...
I agree with others that it is a straightforward exam, with the scope narrower than that of CCNA. The exam material maps rather precisely to the blueprint. (Hopefully this is not a violation of NDA?) I'd say that the main focus of preparation for anyone taking the exam should be VPN/encryption - you should have a very clear understanding of site-to-site VPN - how it is established step-by-step, what main characteristics of each VPN-related algorithm are, etc.
Used materials:
CBT nuggets - IMO, rather basic and not going deep enough (but entertaining

) YMMV.
Official Cisco Study Guide - I only got to read a couple chapters, but really liked the book - perfect coverage/depth.
Mike's notes - condensed format is great for reviewing command syntax.
Lab:
1. 871 router with 12.4T advipservicesk9 IOS - this one router alone covered about 70-80% of hands-on practice needed for the exam
2. Additional 831 router with 12.3T k9o3sy6 IOS - used together with the first router for Site-to-Site VPN, which is ~10-15% of lab practice.
3. 2950 switch with 12.1(22)EA IOS - used standalone for Layer 2 security, another ~10-15% of lab practice.
These 3 units fully covered the blueprint, and I want to emphasize that all you really need is 1 x 12.4 k9 IOS router, 1 x 12.x k9 IOS router, and 1 x 12.x IP base IOS switch.
I will likely continue the CCSP/CCNP:S path. And right now deciding whether I should take a break or try to squeeze SNRS in before VMware class starts in April... I'd have no doubt about biting the bullet if March was not filled with important family celebration dates...