This is not something I want; if a product I use is available only via a web site and the company goes under, the product goes away with it. If it's installed on my hard drive, I can keep using the product.
I'd probably forget about it for that reason too. I mean, literally forget.
My bookmarks and bookmark toolbar are littered already. If I could download it I'd have more of a chance of being reminded to see it and use it. Plus I'd feel it'd be more secure, and I'd be able to work when offline (e.g. commuting/travelling), so I wouldn't use it for those reasons.
It looks like it has some interesting ideas though (I especially like the look of the nested debugging thing with probes).
This is not something I want; if a product I use is available only via a web site and the company goes under, the product goes away with it. If it's installed on my hard drive, I can keep using the product.