I purchased one of the AT&T refurbished GST for $200 and didn't even think about the Outlook connectivity. I just assumed that Outlook would work. Well, it didn't work fully right out of the box for me.
My company's Outlook I guess isn't "normal" in that the server I get mail from isn't the same as the email address so the built-in Samsung email client can't send email with the correct reply address. For example, my email address is "first.last@company.com" but the mail server is "mail05.domain.company.com" and my login info is "domain\flast" where "flast" is first initial and last name. The built-in SGT email client insists on my email address being "flast@mail05.domain.company.com" and puts it into the reply address and makes replies not work correctly. If there is a way to override this I can't find it.
It's fairly decent other than this. It does threading which is something I haven't found on other email clients. It integrates calendar and contacts with the native interfaces.
There are other email clients from the Market, obviously, but I haven't found one that is better than the built-in SGT email, except that they do allow me to setup my Exchange correctly without causing me reply address pain.
If your brother doesn't have a "strange" Outlook setup like me then he might be pretty happy with the stock Samsung email client. I would if it worked. It's not quite up to the iPhone standard that I'm used to (my primary phone is an iPhone4), but it's far better than the generic Android email client.
Hopefully the Gingerbread update will bring more goodness to the GST, but who knows if/when that will happen.