Texting is one of those things you have to get used to and for a frequent texer it might annoy you initially. Most people get used to it quickly and find they can type pretty damn fast in the end.
The keys are pretty small and take some getting used to however the phone does have a pretty amazing corrective checker that auto corrects almost everything you write. Honestly sometimes it works like magic knowing excatly what you want to say! Sometime it wrongly corrects words but like any phone you slowly train it to learn the words you use (if they are not in the dictionary).
If you are worred about the keyboard watch the video:
http://www.apple.com/uk/iphone/getti.../keyboard.html
Should put your mind at rest.
Just to let you know, I don't think you will be able to download emails with a hotmail account. Microsoft I believe disabled the ability to do that using POP a few years back as it wasn't making them any money?
The other accounts should be fine though. Investigate to see if they can support a method of transferring email called IMAP. If they can then that means you phones emails and your emails online will stay in sync. ie. delete an email on the phone, it removes it from the server. Read an email online....it appears as read on the phone. etc.