Opera.Which is widely regarded as the best browser for a phone
Opera was nice but the OS and hardware wasn't up to the task, e.g. adding, editing and removing bookmarks was slow and painful.
I don't notice the drop in resolution. The screen on the Diamond is too small to read anything when zoomed out. The Touch HD would be better though. I still love my Diamond though. Hasn't been turned on since I got the iPhone but still have the centre spot on my gadget shelf sat inb it's cradle

The HTC Diamond was a dog
That's been the case with all my previous WinMo devices (5+). Always a shortage of RAM and CPU power.
The devices have finally started to catch up this year but I got impatient when the 3GS was announced

