I have been using black berry 7230 for some time and finally got the new BlackBerry 8700.

The following are my personal experience in using the BlackBerry.

Pros:
It has the best technology in the world which has made BlackBerry famous around the world. The push technology is definitely ultimate for people who are on the move and want to be in touch with other people by email without logging into any website or internet. The older BlackBerry phones, although not really as good as the ones from major manufacturer like Sony Erickson, Nokia, and Motorola. But one could ignore it as the technology which BalckBerry had would overide the problems in their phones.
But the launch of new BlackBerry models has definitely improved the quality and durability of the handsets. They also have very clear screens now. The size is pretty good and fits into the pocket or you can side it in the pouch (which comes along the BlackBerry) and slide it in your belt

Cons:
The roller ball is still problematic and the more you use the more it sticks deeper into phone. The roller ball does help in easy scrolling on the phone. But one is heavily dependent on this little roller ball and it tends to get over used and causes problems after using it regularly. The main problem is that the roller ball slides inside the phone. The other problem is the support. I had my Blackberry under warranty when it broke down and had to wait for two months to get he device replaced. Maybe the problem is that RIM (BlackBerry Company) is Canada based company and has little presence in Europe and most of the selling and support is done through dealers or operators.

My experience
Although a bit on the heavy side, but aren’t all the PDAs heavy in size and bulky? The battery lasts quite longer this time. There are remarkable improvements in software. Software was always the best in Blackberry across all the phones. It has a impressive full Qwerty keyboard. It really works across continents. I had travelled extensively in US and it did work across without me changing any settings. The same was applicable when I visited Asia and it was connected throughout the journey and I could get all the emails almost instantly. This was a big plus for black berry user like me. This is the first time in my life that I had uninterrupted emails during my travels....A big Plus for me. This is called quad band. It is pretty good in handling calls and has all the ringtones available for a business user (built in) and of course one can download as many as he wants.
It has a built in speaker for hands free chat, which was missing from earlier BlackBerry models. Sending SMS and emails are rather simple like the Microsoft Email and the SMS can also be sent in the same format except one has to change the format to SMS or email while sending it. It also supports MMS. One specific point was the clarity of the phone calls. I have used some major established phones in the past and was surprised to see the absolute clarity in the sound. This is coupled with far reaching reception. It catches signal where most of the phones fail.

Earlier whenever I used to travel overnight, the first thing after checking in the hotel was to open the Laptop and get the internet connectivity to download the mails. Now it is the thing of the past, as I can very easily even download the attachments. There is an option where one can either download the attachments or ignore them. Anyway another copy of the same mail is later downloaded on my PC/Laptop.

I would not like to go and list the features of the phone here as you can read the product details at the company website or anywhere on the web.

Conclusion
BlackBerry has become very important to me and there are some more reasons as well. Firstly it is real business phone, secondly it is wonderful for people who are travelling and need to be connected by emails (not internet).
Please do note that one needs to have a subscription for voice and data from the operator and they are separately charged. The charges for data do vary according to the amount of data downloaded or it also has a flat fee.
I would recommend this type of handset for a business or for people who travel overnight quite a lot and not for teenagers or casual users or for people who love to play games and listen music or for people who are interested in snapping photos.