I can download most any file types from Safari on my iPad. I think the key is to have an app like GoodReader or FileBrowser that handles any file type. Only thing is, there is no download progress indicator, and I'm afraid if I switch out of Safari or even switch to another tab, it'll interrupt the download. So I just stare at the page and hold my breath, lol. But I've managed to download quite a few files this way, including exe, zip, and dmg files.
Of course, you can also download files to your iPad by using GoodReader. That's a better method for larger files.
I don't often use the iPad to do serious work, mainly because the screen is too small, and positioning the cursor to select and edit text is a pain. But if I absolutely had to, I'm pretty sure I could do 99% of all my computer tasks on an iPad. For some of those tasks, I might need to purchase an app. But I think a lot of people who say iPad can't be used for serious work is thinking of what you can do with just the default apps. They don't realize that there are lots of apps out there that vastly expand the functionality of iPad.