I currently own an iPad and I use it mostly for school. I study math so I have a need to be able to take hand written notes. Since I also need to write papers for other classes, there is a need for a keyboard. So if you are going to use this for school, be prepared to invest in some accessories.
First, protection. I have a gel case and a clear cover on my iPad to protect it. Well worth it but not completely necessary if you are on a budget.
Next, get a wireless keyboard. I purchased the apple blue tooth model. To prop up my iPad, I use a book stand. It is a small portable metal bookstand that I purchased at the student store for $5. This way I can type on my iPad while it is propped up on the bookstand (and the gel case actually keeps it from slipping off of the metal bookstand).
Next you'll want a stylus. The pogo sketch stylus works GREAT in apps like Sundry, Noterize, and Penultimate (three I have purchased). My favorite of all of those is Noterize but you should make the decision on your own.
Now the apps. I cannot get by without Goodreader (which now supports annotation), Noterize, and Documents to Go Premium (although, they stink for powerpoint so you may want Keynote). If you want to type any math what-so-ever on your iPad you'll need the LaTeX app for $9.99. Due to Apple restrictions on apps, it cannot compile - I googled online compiler, paste my code then download the pdf into GoodReader. This just does not work for Tex files with images since you cannot upload the images onto the web from the ipad (so you'll want to compile those at home).
I did spend some extra $ for all of this but it is well worth it. I take class notes with my stylus in Noterize while recording lectures, I type papers in DocsToGo (which has Dropbox and Google docs support), I write math papers in LaTeX, and I read and annotate textbooks in GoodReader (and I actually found one on iBooks for a reasonable price).
While I still need a laptop at home for backing up my work, etc, this makes my bag much lighter since I can carry the iPad anywhere without a hassle (24 oz vs 4.1 lbs for my Lenovo Tablet PC - and that is without its base). This made for a very heavy load, even with replacing many textbooks with pdfs on my Tablet PC.
The best benefit of the iPad is its battery life. I can go two school days without charging it. When I had my Lenovo Tablet I used to worry about being in classes that were over 50 min since it would rarely make it through an hour and a half class without needing a charge (I had the lighter weight battery). If i dimmed the screen to the dimmest setting, it would last but I would strain my eyes to use it.
A lot of people scoff and say you need a laptop but I feel that YOU need to make technology fit YOUR needs. I made the iPad fit my needs. Hopefully, you can do the same.