I upgraded to iPhone OS v2.0 a while before I got a 3G iPhone (very worthwhile for me, since I spend most of my time outside Wi-Fi coverage now). Since the upgrade, I have noticed a few things which I have not seen mentioned elsewhere.

Continual pseudo-GPS updating in original models

On my original iPhone under iPhone OS v1.x, tapping the crosshair button in Maps used to locate me -- the button turned blue while the iPhone was fixing my location, then turned grey again when done. To update my location I had to tap the button to get a new location fix. Under v2.0, after tapping the button it stays blue, and the iPhone updates my location automatically until I tap again (to turn it grey and switch location auto-updating off) or exit Maps. This is well-known on 3G models, but I was surprised and pleased to see auto-relocation on the original iPhone.

Pause to rotate (walker unfriendly)

Under iPhone 1.x, I could rotate the iPhone to re-orient Safari while walking. Under v2.0 the iPhone does not reorient while I am walking -- I have to stand still for it to notice the change in orientation and rotate. Annoying, as it means I will have to stop in the middle of crowds to trigger rotation.

More switches to iPod.app when resuming music playback?

Under v1.x, after a sync or reboot, the first time I hit the earphone button to start music playback, the iPhone would switch into iPod mode, but I could stop and start without switching into iPod mode. I have a feeling that it switches into iPod mode sometimes now (after I first started and stopped playback), at times when it would not have before. This is unconfirmed, though.

Upside-down for iPod videos

I believe this changed from v1.1.4 to v2.0, but could be wrong about when. In earlier software versions, iPod movie playback only worked when rotated 90° counterclockwise. Alex hates this, as it puts the speakers behind your right hand. With v2.0, iPod movies can also be played back 90° clockwise, which puts the speakers under the left hand. YouTube still only works counterclockwise, though.

Loss of background functionality with apps vs. Safari

I am very happy with NetNewsWire, Twitteriffic, and Instapaper, but iPhone 2.0 doesn't let them run in the background. This means NetNewsWire and Twitteriffic always need to update when I launch them, as opposed to the Mac apps which update automatically in the background. It also means I cannot multitask -- when I was using NewsGator Online and m.twitter.com, I was able to switch between Safari tabs and Mail, and keep them working in the background as I switched to whichever was done. The apps are much better than the webapps, but the regression of having to wait really bugs me. Fortunately it's lessened somewhat by the 3G iPhone's improved update speed.

Another disappointment is that neither NetNewsWire nor Twitteriffic supports rotation. I thought Apple didn't support it outside Safari proper (both NetNewsWire and Twitteriffic incorporate the WebKit engine Safari uses) until I realized Instapaper supports rotation, and Stanza supports rotation (even upside-down, which Safari does not). I'm sure there are real reasons Brent & Craig have not yet provided rotation in their apps, but as I understand it, they are not allowed to discuss them, or how Instapaper & Stanza do it -- even under NDA, despite the fact that this is released software!

On the other hand, reading Slashdot via NewsGator Online stunk. The delay to get each article was very aggravating, and NGO was useless on the train. NNW/iPhone makes reading Slashdot a pleasure.

Also, Remote is great.