A good 16 page Forrester report, via ATG, requires registration.
Is An iPhone Application Right For You?
How to Decide if a Mobile Application Should be Part of Your Brand's Road Map
The size of the smartphone market — and the buzz surrounding Apple's iPhone App Store — has many interactive marketers considering whether they should deploy mobile applications. Early success by some brands might lead marketers to mistakenly conclude that it's a no-brainer. Before proceeding, interactive marketers should clearly weigh the advantages of driving brand affinity, customer engagement, and possible revenue versus costs in time and resources and the potential pitfalls of a poorly executed application....
•iPhone Apps Show Enormous Uptake
•A Mobile App Can Provide Value In Different Ways
•How To Move Beyond The Hype To A Sensible App Strategy
•iPhone Gets All The Attention, But Don't Ignore Other Platforms
•Tools For Measuring App Usage And Success Are Still Emerging ... '