[getonit]

That you used a spreadsheet puts you in an incredibly small minority. His target audience is going to be those that can see (or will instantly recognise when shown) the benefits of such, but without the motivation to take on the hassle(1) of organising it themselves - people who keep it in their heads, or scribble on whatever scraps of paper etc. they have to hand.

Take the endless 'to-do list' type sites as a comparison: They basically offer nothing (or are not generally used for anything) that couldn't be handled by a carrying around a small notepad with a pen shoved down the spine.

(1) Minor hassle it may be, but magnitude means nothing to a great many people.

[imp]

I may be in the minority (not incredibly small though), but if someone isn't comfortable using a spreadsheet, they're probably not going to be comfortable using a web app either. Spreadsheets are pretty ubiquitous.

[getonit]

I didn't mean comfort (although I suspect that it may come into it more than you give credit for).

I meant hassle; effort - should I just scribble notes, or will I spend a couple of minutes thinking about what info I want to record before I see it on screen? I could knock up a quick spreadsheet of the relevant comparison points pretty quickly, but I wouldn't bother if there was a pen and paper in sight. If I already had a spreadsheet that I'd used previously, though, I'd use it again. I'd use the website in question if it was equivalent to that, and free. (Sorry OP, I can't think of anything you could add that would make it worth coughing up for, for me at least.)

It's fickle, sure, and it's a very minor difference in effort. That's what people do when they're not really giving much thought to what they're doing, IMHO and IMHE.