Rated 4 out of 5 stars
The option to open in a new tab is what really won my vote for this one over "Cache View". A nice feature would be an "open all" (only active for new tabs/windows) so you can quickly check hard-to-find pages in one operation. With so many options for engines, maybe even have a checkbox beside each engine to be able to select it as a "favorite" and make the "open all" an "open all favorites" or something like that.
The best thing about these "manual" cach viewers vs. ones that spring up when page load errors occur is that the manual ones work with proxies. :-)