I personally would never go without a real computer. I occasionally use photoshop, like the ability to backup on a cd/dvd or portable harddrive without jumping through a ton of hoops (these t hings are all practically if not totally impossible to do on an iPad), and like the ability to print easily (I'm not a fan of 'buy an expensive printer just to print from the iPad)
for you? maybe it'll work. I'm old fashioned, I like backing stuff up on my own and not depending on a third party service. I'm not a fan of 'the cloud' and perfer to keep my data nice and safe on a portable harddrive where I know exactly where it is and who has access to it. Others feel differently.
I will commit the sacrilege of suggesting that, if you want a light duty comptuer, there are plenty of PC based netbooks out there for less than $500 that could serve your needs. Might be too small for you though. I do agree that the 800x600 screen on my netbook does take some getting used to. but then I think about only carrying around 3 pounds of computer and I deal 🙂
If you want to go with your iPad as your main computing device, I'd look into a keyboard. I have smaller hands and the onscreen keyboard bugs me. And it's not as much the size as it is the lack of punctuarion, handy numbers, etc. I use a Zagg Folio, which is keyboard and case in one and makes my iPad like a mini laptop. There are others out there so it's a person to person thing, but might be something to look into.