Well, pros are that internet is quite faster than on other phones I had, you just need a gentle touch for the screen to register what you want, panning and zooming is cool (), pages look really good (almost likethe PC versions) and surfing is a really plelasant experience

Mail is great, I don't know what to say about it...
You have dedicated application (you get it with the phone) that manages all IMAP and similar data for you- you just pick your mail "provider", type in your name and password and it's set up, ready to use.
You can also activate the option so your iPhone will check for email every X minutes...
Gmail (which I use) works fine. I couldn't ask for anything more in mail...

Cons of iPhone surfing are:
No flash- you won't see some ads on pages- but you also won't see many embedded videos and stuff...
But, if you use internet primarily for mail- it's not big deal.
Also, typing text on the pages could sometimes be buggy, not very often- but it's noticable on some specific sites (so I believe it's their mistake).

For youtube, you have a nice youtube app- that has almost all the options like the "real deal" (real site). You can sign in, view your favourites, subscriptions and stuff like that...

In my opinion, iPhone is one of the best phones for surfing

BTW Sorry for spelling (and other) mistakes- I'm sure there are some