If you primary want a phone for email communication, the blackberry is probably the better phone (never used it myself) for this, but all three can do email well. If you are going to use apps a lot, then the HTC and iphone are better options I think.

Android phones (like the HTC Desire) and the iphone are more "app phones" compared to the blackberry.The HTC Desire has a more powerful Operating System capable of higher levels of customisation. In contrast, the iphone has a more restricted platform, but offers a much more intuitive and easy to use interface.

At the moment the iphone platform has better apps available, and the apps in general are better quality. However, the iphone 4 currently also has an issue with its aerial (the so called aerialgate issue thats been on the media). Opinions are varied about how serious this problem is. 

Both the iphone and HTC Desire are good phones and are likely to serve you well.

HTC Legend is very good also... :)

I had Iphone 3G for almost two years and I loved it. Emails, applications of all sorts, weather, chat, name it and iphone surely will have it and have no complaints from my side.

Recently I thought it's time for a change so moved to Blackberry despite cautious advise from friends. It's one of the best techy decision I have ever made. I adore my new phone.

So what's the big difference? A lot!
1/ I got all my messages: sms, bbm, emails, facebook, chat, calls in one location button. They are all summarized there so all I have to do is check in one place.
2/ Chat messaging runs on the background. Unlike Iphone that to be able to chat, you need to open the application and the minute you close it then you are out of the chat. In bb, sign on and close the application and you will remain logged on and you will receive your messages on this one button i mentioned. You don't have to go to the chat again (msn or ym) to be able to reply, you can just reply directly from the message you received.
3/ BBM - you have friends that have BB? Then your exchanged of messages are unlimited for free regardless wherever they are.
4/ Only a few difference compared to iphone for the applications - you can't chat in facebook, the sbb application is a bit difficult but so far all the rest that I used to have in iphone are the same.
5/ Pictures, both are great!

Iphone and bb they are both amazing gadgets to have.
Happy shopping.

Though note since the advent of iphone 4 OS, iphones (specifically the iphone 3GS & iphone 4, but not the older 3G) can multitask, and handle chat messaging in the background.

At the end of the day depending on who you ask its a personal preference thing, and depending on who you ask, you will get a different opinion, and that opinion may change with time.

For example, one of my friends in Australia bought an iphone 3G when it came out and loved it, then she got frustrated with it, because of its lack of customisation options and its slow speed (as the phone aged, software became faster), then she moved to the blackberry which she thought was fantastic, then after a while she got frustrated with the apps on the blackberry (particular with twitter apps), and she switched to the iphone 4, which she thinks is the best thing since slice bread.

Re photos: The new iphone 4 has a much improved camera they takes much better pictures compared to the older models. Remember, when comparing photo quality, don't focus too much on the megapixel specs - they don't necessarily mean that the photos are better. Check online reviews for better guidance and picture examples.

But to finalise, I think all three smart phones are good, and which ever is better is largely personal preference. Try using all three of them in a shop or try out your friend's, before buying one.

Thanks everyone for the advice!  I see that people are really passionate about their mobiles!

You should definitely look at them all in person. The iPhone4 screen is absolutely amazing (and the phone in general is pretty incredible - I've not noticed any issue with the antenna at all, and in fact the reception is noticably better than the 3G and 3GS).

passionate about my iPhone. I do use apps a fair bit, although v selective. also for music, and lots of podcasts. Also for flicking between various email accounts.  Have a BB for work, which perhaps explains diminished passion for this tool... good for work email, and for batteries. Batteries is the bane of my iPhone - pretty pants

get both... I do, and the BB has better camera ... but iP better apps... I use the BB for work and iP for personal.

Phone coverage and reception is better on the BB....

what about battery life? which one is better?

I've used an Iphone 3g for 2 years now and I'll take a Desire or Samsung i9000 very very soon. I'm an apple addict but i must recognize, from my point of view, that the Iphone is a crap...

BTW, all 3 are good devices and you just have to choose what suits you the best :)

blackberry by a very long shot.... 2 to 4 days depending on use, versus 24 to 36 hrs for the iP.

Actually Charlie, the Blackberry (Torch) wins on standby, but the iphone 4 wins on talk time and in fact everything else (e.g. 5.5hrs vs 14hrs talktime on 2G,  30hrs vs 40hrs music playback, 6 vs 10 video).

I think the HTC Desire is much worse than either, for battery.

Mind you, the blackberry and desire have removable batteries, so in a sense they annihilate the iPhone. But then you can get a battery based charger for the iphone. ;-)

Basically, I have an iPhone4, have had ZERO problems with the antenna and it's easily the best phone I've ever owned or seen. I think the Desire and Blackberry are both fine (though I'd definitely go for a Desire over a blackberry - I hate that fiddly operating system), and what it will boil down to is how much you're prepared to pay, and which one feels nicest to you (hint: it'll be be the iPhone ;-) )

i have the latest BB Bold... and its the best BB i have ever had, sadly my iP is the 3 not the 4... and its a good phone...but the battery needs charging every day, whereas the BB can go a few days...

Anyway IM a crachberry addict, and can type on it as fast as a desktop...

the plus with iPhone though is the easy switch to multiple languages...not a feature of BB... so both have plusses and both have slight negatives...

in fairness for a "pa" phone the iphone is fine, but I wouldnt want to use it for business...

Also, take not of the specific models/versions; because for example, there is very large difference in battery life between the iphone 4 and the older iphone 3G for example.

I use Legend for two months, and im very happy with it. If only Apple was not so restrictive, i would go for the iPhone.