Cappuccino performance on iPhone isn’t satisfying for now, due to the device’s processing power and limited memory (that are also main reasons for the absence of a full Flash version – besides strategic matters and historic poor peformance of Flash player on mac compared with the Windows version). From the Cappuccino team leader, it appears that WebKit team may have discovered a bug in iPhone’s Safari that leads to an additional parsing of each js file, thus requiring twice the time (moreover that step takes half the whole time of a CP application load). Besides that large improvement area (that could be provided soon through the iPhone 0S3.0 update), the Press tool could filter on a method basis instead of on a whole class basis. Indeed some classes such as CPArray include a hundred of methods, that aren’t likely to be used all in a given application. However this could be problematic with dynamic calls, where used methods aren’t known before execution.
Then it is planned to allow deploying Cappuccino applications targeted for various environments (desktop, mobile). A new archive format (that reminds OSX universal binary concept) will be provided (no compilation however there). The Atlas editor could then produce archives optimized for all devices.
Use of Cappuccino for portable applications is a straight choice however, as if performances are a concern, migrating to iPhone SDK would be easy (same frameworks and concepts).