This is something I've considered trying, just as an experiment, but haven't got around to. I'd be interested in hearing how it works out if you go this route.
The tests these guys
did might give you an idea; BobAtkins.com
is a photography-oriented site but it has a lot of CF tests.
There's no issue with reads
-- they're effectively unlimited. It's total lifetime writes
you have to worry about. Flash is a lot better than it was a few years ago, though when you're going the DIY route with CF you're not going to get the benefit of some of the fancier techniques that SSDs use to extend their lifespan (wear leveling, etc). Most of the data in an OS install is read-only, but there are a few "hot" files that see a lot of writes -- most notably the swapfile -- that you have to worry about. But for just a semester, doing homework? I wouldn't worry too much about it. Let's say you're going to be using it 4 hours a day, 7 days a week, for 6 months. That's ~720 hours, or ~45000 minutes. You'd need more than 20 writes a minute every minute, to the same block, to exceed one million writes. That's certainly possible with the swapfile during extensive usage, but I doubt your friend will sustain that.
Slow laptop hard drives are going to be way less than 133MB/s -- more like a third of that. So Flash can be faster, at least on reads. But depending on how the card reader is hooked up, it may in fact be much slower: it may say it can handle Flash that fast, but if it's on a USB port internally (as many are) it's not going to break 40MB/s anyway. In which case you might as well just get an external USB harddive (or, better, an external USB housing and a hard drive you buy yourself). Or Firewire, if the laptop has that and you can afford it.