For every person who has ruined a saddle or boot with neatsfoot there are probably thousands who haven't. In my experience, every time this subject comes up in these forums there are a lot of folks predicting dire consequences who are just repeating what they've heard elsewhere. I personally have treated my brooks saddle with neatsfoot (glove oil) with no ill effects. Sheldon Brown, who has more experience with these matters than most of us recommends neatsfoot (http://www.sheldonbrown.com/leather.html). If you want to spend the extra money on Proofide in the belief it is a superior dressing, you are free to do so but, as Sheldon points out, you are more than likely prolonging the break-in time unnecessarily.

By the way, tallow is what you get *after* you render beef fat. It's full of oil which can be separated from the solids by pressing it out. Or you can just heat the tallow up to liquify it then cook your fries. It works just like lard and it should since they are both produced by rendering fat (pork = lard, beef = tallow). Tallow has a melting point of about 104F (40C) so unless you heat your saddle so the Proofide will soak in, a lot of that magic juju you spread on it will sit on the surface just to be wiped off by either your bike shorts the next time you ride it or the towel you use to wipe the "excess" off after "treating" it. That's probably why it takes so long to break in a Brooks if you just use Proofide. Very little of it is actually penetrating the surface of the saddle.

Oil is what protects the saddle and keeps it from drying out and cracking. The wax in Proofide provides some waterproofing but just until your bike shorts rub it off. It's the oil that does the bulk of the work, though.