Exchange or Gmail
Some of the account types offer even more advantages. For example, Exchange and Gmail accounts offer a good alternative to IMAP with some additional benefits. If you have a Gmail account, or a Microsoft Exchange account--like an Office 365 account--you can sync in real-time with your email and calendar (and contacts for Exchange).
Using Gmail or Exchange, you can access your entire mail account--including sent messages, and all of your folders and subfolders. So, even if you moved the email from last week with the crucial client data to a different folder called 'Crucial Client Data', you would still be able to access and retrieve it from the iPad as long as you have an Internet connection.
Another advantage of using Exchange or Gmail is that your messages are already scanned for malware, spam, and phishing scams, and those messages are filtered out so you don't have to sift through them in your Inbox.
iPad Mail Pet Peaves
Apple has made some significant improvements to the Mail app over time. I appreciate that I can have multiple email accounts and view them all simultaneously with All Inboxes, and I like the threaded conversations that make following a stream of messages more efficient.
However, I am not a fan of the spam. When I set up my email accounts using POP or IMAP, I get all of the email messages in my Inbox--including spam messages about low interest loans, and guaranteed penis enlargment. If I go look at those same email accounts in Microsoft Outlook, those messages don't make it to my Inbox because the Outlook Junk Mail filter catches them and filters them to a separate box.
I also don't appreciate the lack of groups or distribution lists. I have a variety of distribution lists set up in Outlook that I use frequently, but with the iPad Mail client I have to manually add each individual email address every time I want to send an email. It would also be nice to be able to do simple things like make text bold or italic, or insert links into the message, or add file attachments.
The Mail app is decent, and it is way better than it was in previous version of iOS, but it still has a long way to go to rival what I am accustomed to with Outlook 2010.
Changes in iOS 5
iOS 5 will be here in a few months, and when it is released there will be some pretty significant changes to the Mail app. Here is what the Apple iOS 5 site has to say about the updates coming to Mail: "Your inbox is about to receive some great new features. Format text using bold, italic, or underlined fonts. Create indents in the text of your message. Drag to rearrange names in address fields. Flag important messages. Even add and delete mailbox folders on the fly. If you're looking for a specific email, you can now search in the body of messages. And with iCloud, you get a free email account that stays up to date on all your devices."
For my purposes, I am setting up my personal and business email accounts as POP accounts within my Gmail, and then using Gmail for sending and receiving messages on my iPad and iPhone. It gives me more flexibility and is easier to manage, while also providing spam filtering and phishing protection.