Hi J-J.
Like you said, I also have to charge the phone every night when it is switched to the 3G and 2G network option. To solve this, I set the phone to ONLY use the 2G network, and manually switch to 3G when I need it . This gives about 2 - 3 days without recharging.
As far as I can tell, there is no way to backup the downloaded apps. This is quite frustrating, as I recently had to do a master reset on the phone and lost about R100 worth of software I downloaded from VLive.
About the missing features, this is something you'll have to take up with Vodacom, as the Vodafone firmware on the phone doesn't allow you to:
1) Use any MP3 as a ringtone (without having to modify it using a SE DRM Tool)
2) Have Photo Caller ID on the external screen
3) Use SE's instant messaging client ("My Friends").
As far as I know ALL of these features are advertised.
I have resorted to converting my V800 to a Z800, by installing the Z800's firmware on it. The V800 and Z800 are EXACTLY the same physical phone, with the V having Vodafone's firmware on it and the Z Sony Ericsson's. Of course, this probably voids my warranty.
Some things I've noticed with the Z800 firmware:
1) Allows external screen Photo Caller ID.
2) Any mp3 can be used as a ringtone.
3) Gets rid of that yucky Vodafone interface, and replaces it with the standard Sony Ericsson interface.
4) Solved some Bluetooth problems re. handsfree car kits for me.
5) Data Connection is muuuch faster. (time it takes to connect to GPRS / 3G)
6) Better 3G signal reception.
7) Longer battery life when switched to 2G and 3G mode.
8) Allows use of the instant messaging client (Which works GREAT!!)
9) Takes away your VLive! Access. (working on getting that restored)
I'm am VERY glad I made the switch. I do not at all like the Vodafone branding on the phone. Some menu structures with the Vodafone firmware were also structured to make it easier for you to spend more money. Ie. When you want to write an SMS, the FIRST option that comes up after you choose "Write Message" is the "Picture Message(MMS)" option, and NOT the text message option.
As for the missing features, I think Vodacom SHOULD address it with a Firmware upgrade. On the other hand NO Vodafone branded V800 in the world offers these features. They are only available on the Z800i.
For the moment, I do not regret voiding my warranty to get, in my opinion, the phone that the V800i was suppose to be. Also, I don't think that having a choice in firmware on your phone (which provides a better feature set) and applying that choice SHOULD void the warranty... especially on the hardware components of the phone.