Review: iPhone 3GS

It sounds like your current understanding is correct.

The iPhone does do a decent job of pseudo-multitasking. It's not actual multi-tasking, but most apps do load quickly and pick up right where you left off, which is most of what multi-tasking is supposed to provide. With third-party apps, it's up to the developer to make this work seamlessly, (a poorly-designed app would not pick up where you left off,) but Apple has created a system that will work well for most.

The real missing feature - as benjitek noted - is the ability to run apps in the background. Apple "cheats" and lets its own apps - like iPod and now Voice Memo - run in the background, but won't let third-party apps do this. There are all kinds of potential apps that might make sounds, listen for sounds, stay connected to the Internet and wait for messages/events, etc.

For that last category, Apple is trying to provide that functionality via Push Notifications. Apple says this is a better way to do it, and there are some advantages, but it's also limiting, because developers have to work within a very specific framework that Apple is providing. There will always be more possibilities if apps were allowed to run in the background.