I've had a year with the i300, preceded by the Kyocera 6135 and the PDQ,
and various Palms and non-Palm phones before that.

The i300 is a terrific integrated solution, with only one major problem:
the display. That is, the screen cannot be seen in direct sunlight, and
even in the dark the color saturation was poor -- all pastels. It was
nevertheless better than the monochrome Kyo 6135. The Palm functioned
just like any 3.5 unit; well.

I bought the i330 the day it reached the store, and after a few days
find it to be absolutely outstanding! Memory was doubled to 16MB
(non-expandable), the display is bright/sharp/colorful and usable under
*any* lighting conditions, and everything "works." The functional
changes correlate very well with consumer comments on the smartphones
forum - indicating either remarkable intuition by the engineers, or they
read the commentaries and designed accordingly. Examples: 100%
programmable buttons, selectable vibrating alarm, improved speakerphone
control. It's a bit smaller/lighter than the i300, and has a nicer
"feel."

My favorite Samsung feature was retained: voice-dialing. That is, I can
keep the phone on my belt, and either accept or make calls with a button
on the retractable earbud - I rarely touch the phone on the road.

There also seems to be a difference in the RF front end, as in driving
past a specific drop-out point along a nearby interstate, it held the
signal while its predecessors (3500, 6135, i300) consistently dropped
out. I went to the trouble of a couple of u-turns just to check - and
used the absolutely-certain outside lane - and either the phone is
better or Sprint put up a new tower overnight. Another bit of evidence
is that the phone so far works in the car while on my belt, below the
window line - its predecessors had to be stuck to a gizmo on the dash.