This is going to be terribly short.
1. The iPhone 3GS sounds better, through the UE11 Pro, than the iPhone 3G (3.0 - not tested with other firmware). It's noticeably better - a sufficient improvement that it's probably worth an upgrade if you listen lots.
2. I marginally prefer the sound of the iPhone 3GS, through the UE11 Pro, to that of a Sansa Clip 4GB (Revision 1 with firmware 01.01.32). For reference, I preferred the Sansa to the 3G, but stuck to the 3G for most uses for convenience.
3. The iPhone is, as previously mentioned, noticeably faster. This improvement means that reading an RSS feed or surfing, while listening to music, is almost entirely lag free. This is very nice.
To be clear, the audio comparisons are of the headphone out, without external amplification, of EAC-ripped, LAME encoded 320kbps CBR mp3s. Sorry that I'm not using a lossless format :p
