Here are some features in detail (apart from what can be taken off from the official website)
About connectivity 3G, Wifi, USB Teethering (allows your phone to be a modem). No issues with connectivity as the unit is able to surf using wifi or 3G. No issues with Celcom Broadband or Maxis BB or using my wireless router at home.
About its Web browserThis is a no frills browser : does not support flash so no youtube and no farming on farmville either! If you intend to visit multimedia loaded sites - use your PC

Sites like twitter automatically recognises your phone and sends you to a lite-twitter page. Facebook fans can go to m.facebook.com for a lite weight page. It loads the normal facebook page fine btw - only that the screen gets crowded and you will miss flash.
About its emailSupports IMAP and POP. Cinch setting up for yahoo, gmail accounts since it is automated. I had no issues connecting to my office email account as well. You can set as many accounts as you want but you cannot choose to disable temporarily any account other than to delete it. So if you set 5 accounts - it will check all 5 accounts in sequence.
Attachments supported : image files, pdf and word. Pdf and word files are browsable. The unit cannot open the newer MS Office docx format. Doc and txt is fine. Pdf files are fine. Had some issues with documents scanned in low-res pdf but fine quality pdf should be no problem.
Email message limit size is 5MB. Anything larger and the phone will not open the message.
About WeatherNo biggie. Weather for the week from nearest location or a location of your choosing. The weather info will be tied to your Calendar so the week's calendar items will have a small icon on the weather forecast for each day.
News ReaderNothing spectacular - you can add various RSS feeds for the new reader to update abbreviated news snippets. News item can be launched by the web browser if you wish to see the complete article.
About Flight InfoYou can check arrivals and departure by airport or by carrier.
About CalendarSyncs with Outlook. The syncing process is on the slow side. Synches contacts, emails and to-do lists.
About File ManagerThere is no file manager function. You cannot load pdfs or docs which you wish to read on the phone. The only way to do it is to attach by email.
There is no cut & paste function. The only time it is available is to C&P phone nos. to be added into Contacts. Contacts size is 5,000. On my first firmware upgrade it warns you to backup your contacts as the list was erased. Not sure if future SW upgrades will result in contacts being erased.
Typing with QWERTY is fast but my pudgy thumb will always mistype the U,I and Os. Otherwise no complaints. Also the autofill works a treat and makes typing faster.
There are no fancy apps to install. No IM apps etc etc. The phone features are as what it comes out of the factory.
About its battery lifeIf you surf on wifi a lot - the battery can die as early as 4 hours. I set the brightness on 45%. It defaults to 100% when its in car cradle mode. In bright sunlight, brightness needs to be @ 90% or higher to be viewable. Indoors 40% more than enough. Standby time is reasonable.
About its camera3mp allowing for geotagged photos to be taken. As a mapper myself - this function allows quick harvesting of roadnames, POIs, postcodes, signages without having to dabble with pressing enter - using keypad - scribbling on notepads. Quality is image is OK. Very good in bright sunlight. And its nice to actually be able to take a picture of a nice vista, durian tree, a beautiful creek whilst out riding on the mountain bike and know exactly where i took the pic. Just don't expect the pics to rival any of the digicams out there. For my purpose - more than OK.
About its GPSVisual interface of the 765. Including the seamless scaling zoom feature (very nice). I can confirm the following based on my email exchanges with Garmin:
It has : Junction View, Lane Assist, Exit Info. Current firmware does not support 3D Buildings. No plans for support.
What is different about its GPS vs 255W?Vectorised 3d display and address parsing and find your car. Surf a website, find its street address - just click and the gps will find the street. See images below to understand how it works. I have not posted how JCV looks on the Nuvifone because I am lazy to reinstall the 2009.5 (JCV version) on my unit and now using 2009.30 Beta (minus JCV)

Note that address parsing DOES NOT work with any map as it requires a dedicated config file. Without the config file, you can click to search for address but it will return no results (even though the road you are looking for is in the map).
CIAO!I didn't subscribe to this service. Basically it will beam out your locations regularly for your friends to know where you are. If you have 100 friends with Nuvifone running around KL with CIAO, then you should be able to see 100 dots telling you where they all are. For all you know, one may just be 1 building away. Good for locating beer friends, biking friends, lepak friends, BPL kaki's but not so good if the wifey has one too ..
Find your carThe moment you uncradle your phone, your unit will remember the location. So as you walk around shopping or whatever - you will see a new icon on the map : red car which will indicate where you last parked your car. Suitable for the location-challenged types like wives and girlfriends who cannot remember where they left their cars.