According to Palm's website, you need the update if you see Treo755p-1.04-SPNT under Phone Info. The update will take approximately 45 minutes.

Here are some tips before you start:

• Install this software on a Treo 755p for Sprint only. The update will not work on any other Treo smartphones.
• Allow an hour for this update, preferably at a time when you won’t be interrupted by phone calls or text messages.
• Be prepared to back up your data before the update and restore it after. The updater itself will take approximately 45 minutes.
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• Important: Settings for some applications such as IM are not retained after update process. You will need to re-enter your user data. If you use Email (VersaMail) remember to re-enter your email account password(s).

You can get the update here.

Update: Hmmm, I was just reading through the 755p forum thread and noticed that forum member reverendrhino has come across a couple of changes with the ROM update so far:

Green/orange-ish directional arrows for texts. green for incoming, orangish for outgoing.

Under BlueTooth>Options... there was Bluetooth Audio. now the option has disappeared from my menu. i tried it twice, it came back, disappeared, then came back and is now gone. It appeared to be A2DP software but i have no means of testing it now, all the resets in the world havent brought the menu function back, as well as BT on/off, visible/invisible, etc doesnt work to bring the menu item back that simply said "Bluetooth Audio"

Forum member spiVeyx said that Blazer seems a bit faster, and switching between programs seems to be a bit more snappy.

Get this, a couple of folks even mentioned putting the ROM update on their Treo 700p! I thought that was very interesting. ;-) I'm anxious to see how that works out.

I was looking at the thread again just now and read that Andrew over at Treonauts has listed some other changes showing up after the ROM update. Like Andrew said, it looks as if Palm has incorporated many of the changes first made on Sprint’s Palm Centro. You can see Andrew's list here.

Power Saving Mode (Image above left)

Palm has finally executed on the suggestion that I had made at the time of the Treo 680 launch regarding the matter of turning your screen OFF during calls in order to enhance overall battery life.

Now you can simply go to Preferences > Power and set “Backlight during calls” to ‘off’ and thus increase your talk time by having the screen turned off during calls. Pressing any button during a call will bring the screen back on.

SMS Short Code Translation (Image above right)

Another new enhancement now allows you to simply enter the word ‘yahoo’ or any other 4, 5 or 6 digit alphanumeric into the SMS ‘To’ line (image above right) and your Treo 755p will automatically translate this to a 12-key numeric equivalent.

Even though listed among the changes is the ability to turn your screen OFF during calls, a couple of TreoCentral forum members have stated that they cannot do that. A few people have mentioned that their 755p seems snappier now and that switching between apps is quicker, and that the white screen waits while switching apps has significantly decreased. Blazer is also said to be quicker.

Discuss this in our forums.