Flashing the v3c firmware should not to be taken lightly. As with any decision there are numerous pros and cons towards flashing.
-Pros
*Faster phone reaction (with the Verizon flash, the phone has a delayed response from button pushes)
*Bluetooth Object Exchange (transfer contacts/pictures/ringtones to and from computer to phone over bluetooth)
*Bluetooth Object Push (transfer contacts/pictures/ringtones to another phone over bluetooth)
*Longer battery life (the Verizon UI uses too much power, even longer battery life if you disable EVDO)
*Low battery beep is silent in vib and silence modes
*Phone can be charged on Apple Mac computers
*Motorola UI (No more red bars)
*Menu items can be reordered
*Ability to skin (meaning changing the colors, pictures, etc etc)
*Customizable home buttons (four arrows +2 soft keys and smart key)
*"Vibrate then ring" profile without seem edits
*Much better mp3 player (playlists, fastforward, pause, play with lid closed)
*Camera has more options
*MPT all options work and are enabled. (mms, calender, sync, phone book)
*MPT internet connection (connects at 14.4, 1x, EVDO speeds)
*Added "Battery Meter" display under "phone status" menu gives battery life on a scale of 1-6
*Phone status bar no longer appears at bottom of phone on outside LCD (no covering up of time)
*Text messages: can be scrolled thru from one message to next (no exiting message to read next in line)
*Voice dialing does not ask to choose from "Mobile" or "Mobile 1" (a problem on the Verizon firmware)
-Cons
*Voided warranty (if Verizon were to somehow find out... doubtful if you're good )
*Possible damage if you screw up
*No PRL updates over *228 (will disable data services on the phone)
*buggy interface (mostly fixable but still some bugs numerous seem edits required to get EMS working easily.)
*Search Function in phone book only jumps or finds, (verizon UI combined the 2 together)
*No fullscreen picture mode (pictures only take up about 2/3rds of screen)
*No picture editing (crop, resize, draw)
*No Fun frames
*Pictures taken w/camera don't fit screen well (stretch pixelates them some)
*No "World Clock"
*No "Note pad" wait, notepad is there, under recent calls->notepad
*"Missed Calls" menu no longer there, all calls lumped together under "Received Calls"
*GIN / Mobile web broken (fixable via wiki instructions)
*GIN icons gone (fixable via the wiki instructions)
*Text messages: inbox and outbox limited in size (says low on memory at around 50 to 60 messages, recent seem edit allows 100+messages)
*Text messages: when "reply" to other verizon customers they defalut to "delivery confirmation" "yes" (seems to only be on some phones no clear fix for it yet)
*Font Size is bigger than Verizon GUI although this isn't necessarily a problem
*Double Date appears on lcd (Alltel 03 firmware only)
*Reported loss of bluetooth connection to hands free device (Alltel 03 firmware only)
*Moble web times out upon initial access (Alltel 03 firmware only)
Some things that can be accomplished without completley re-flashing
Outside lcd (applys to all firmwares via a seem edit)
Edit "Verizon wireless" from inside and outside (applys to all firmwares via a seem edit)
Reenable bluetooth object exchange (applys to verizon 03 firmware via a seem edit)
Free WAP (all firm wares). VZW .02 firmware has basic OBEX file transfer support (no PUSH).
"Vibrate THEN' Ring" enabled (applys to verizon firmware via a seem edit) **no vibrate AND ring function that I know of yet**
Enable "Call guard" (applys to all firmwares via a seem edit)
Enable various built in ringtones (all firmwares via a seem edit)