If you have never used a BBerry and buying it using your own money (as opposed to being reimbursed by your company for buying one), this is the best model.
Also, most buyers will be considering between 8520 and other Nokia e-series phones (e-63, e-72 etc.). So I want to clarify a few aspects:
Nokia phones (any model) use a Symbian OS that is more than a decade old. This is a very slow OS and has lot of problems. I was using an N-72 and it was painfully slow.
The push mail that Nokia advertises isnt exactly a push mail from a technological point of view (for the interested people, Nokia uses IMAP IDLE protocol which is a sophisticated pull mail that looks like a push email.
Anyway, at a price tag of INR 11, 650/- this is the most powerful smartphone in the market. The push email is lightening fast, in fact I have almost given up accessing my emails on PC. The BBerry OS (version 5) is light years ahead of Symbian platform. The new BBerry Torch has OS version 6. I wonder how greatly efficient it is going to be. I have not used any Android yet, so I can not compare BBerry OS with it.
The QUERTY keypad is smooth and reliable. Voice clarity and data transfer is excelent. The camera is 2MP and gets the work done. Anyway, if you want to shoot professional quality photos, you should not be using a mobile camera in the first place!
BBerry App World may not be as rich as Apple, but has enough applications to take care of your personal and professional needs. The only hitch here is that any application must be installed on the phone memory (which is 256 MB; why RIM?) and this effectively limits the third party applications that you use to about 6-8 (or may be more, but not too many). So, the 2GB SD card is purely a mass storage device.
BBerry browser is good and fast, but the image quality is a bit lower than Opera Mini, dont know why. Or may be I am missing some settings here.
All popular social media applications (Facebook, twitter etc.) are easily downloadable and work smoothly and quickly. Just like email, I am on the verge of quitting facebook use from a desktop :-)
Battery is a weakness and needs a full recharge every day. Quite natural given the kind of functions and data transfer this device does.
The user manual is useless! You will find much better help in online forums and blogs. The desktop software takes ages to get installed, and still does only basic stuff.
To sum it up, if you want to buy a smartphone and dont have the budget for the really high end ones (INR 20K plus), this is it! And even if you have a higher budget, do buy a BBerry high end phone only.