Pros: Insert, Balance, Offset
Cons: I still don't sink 100% of my putts
Know first that I do indeed have an Est 79 TM-770, but mine is a satin finish. It is the old "Fontana" style.
I think the insert is wonderful. Never really felt anything like it. It's a Surlyn insert, a material that covers most golf balls, so perhaps the interaction of similar materials is a positive. The texture is of importance as well; it supposedly gets the ball rolling much quicker than a flat faced putter, which could cause a ball to skid on the green. And yes, I was able to feel that difference on the putting greens today.
This is a completely face balanced putter, which I'm told favors my straight putting stroke (as opposed to open-square-closed stroke). The highly similar TM-880 is perhaps the putter for you if you prefer a toe balanced model. Both models are ever so slightly offset, a feature I've grown to like. Now I hit the ball when I expect to hit it.
The look from above is simple, classic. Past putters of mine look like Andy Warhol paintings in comparison. No need for putters with fancy castings or visual distractions *cough*ScottyCameron*cough*... just a stick that gets the ball moving in the direction I intend it to.
It's an average weight putter, which more importantly looks as heavy as it feels. Putts feel really good coming off the face. When it makes a mistake, it's my fault.
I guess you can't go wrong with an old casting that's been around for decades. The ol' Fontana - hopefully this is the beginning of a good relationship.