The iPhone definitely opened a lot of peoples' eyes to the possibilities, although Apple's tight grip on iTunes as an application distribution channel limits some of the opportunities. I see a lot of talk about companies wanting to develop apps on Google Android, but are waiting to see what new devices beyond the G1 become available. I also hear a lot of great things regarding the Palm Pre as a computing platform, but they will need to get with a carrier other than Sprint to be successful.
The #1 limitation for all of these devices, however, is the limited battery life of each device. Can't use them for mission-critical apps if they have to hit the charger every 8 hours...