If you are going to speak a lot, do not get a Blackberry, The phone features are poor and the battery's run down very quick.
It starts to get annoying after a while. The battery is much stronger in an I-Phone as it's designed to function as an MP4 player as well, and also runs more powerful gaming applications, if you use neither you could happily chat for hours and not notice the battery going down.
I'm p'eed off with my blackberry. The Windows Mobile is great as is the office applications which all run fine left on for hours, but the minute you start talking on it for a couple of hours the battery goes flat very quick. The annoying thing is when you get to one bar, instead of warning you and saying battery low, it cuts off the phone application and means you get no coverage and have to charge before making a call. This can be higher frustrating especially if you don't notice it and get people saying they were trying to ring you.
The I-Phone can't be unblocked as far as I know at present as well, so has to be used on O2 who are very happy to overcharge for its media applications, I.e Facebook I Phone application, mobile internet and windows services.
The best deals you will get are with T Mobile, but this is Blackberry only.
It's more an office use of phone, one to send and receive emails, scroll the internet, check planners and things like that. The best thing is you can sync with your PC with a Blackberry, so copying over all emails from Blackberry to PC and vice versa, a great tool and also with Internet Media application you can store your passwords and bookmarks.
I must admit the Betfair Mobile application doesn't run very quick unless in a 3G area. Another cool thing is you can use it's 3G capabilities to log onto the net via your laptop, using the Blackberry's net activities, however I must warn most mobile phones will charge you a set rates for mobile internet, and its a different frequency to use the Blackberry to connect online via a laptop and you will be charged per mb used. Trust me this is not worth it for a train journey say, I used 31mb of browsing whilst on the way to London a few weeks ago and found out it cost me £45 roughly, around £1.50 a mb, a sneaky thing O2 forgot to tell me, but gave me no issues in moving over to T-Mobile.
I love my Blackberry but the battery is poor, however the I-Phone is more kiddy and for the fun applications, rather than the internet, email and such of the pluses of a Blackberry.
Someone has told me the Samsung phone of the same mode is top notch but I haven't tried it, not sure if that's been unblocked for all networds yet.
I have the Blackberry Curve 8310 by the way.