I use it and love it.
The biggest thing affecting page speed is not file size, but the time spent waiting for a server response for each file. If you have a complex system, this can be the vast majority of your load time.
www.webpagetest.org -slower than most internet connections but it's good for test consistency (within a few hours).
Total cache allows you to automatically combine JS and CSS files. In fact- don't go off of Google or Yahoo's! page speed scores - focus on your actual load time- minifying and compressing JS and CSS might save off a second or so, combining those files will save you 5 +
If you are lucky, all of your JS and CSS will combine perfectly without effort. If not, you have to do a lot of manual work picking out which JS isn't compatible. If you don't have time, Cloudflare's JS manipulation goes 80% of the way.
Finally, Total Cache will use the op-code cache for things like database calls and objects, etc. I don't think the other caching plugins do that.