Always consider the source. Ted's comment on the SF does not reflect my experiences with the model (I have eight of them and they all perform similarly well), but his opinions are worthy of respect and I'd be inclined to believe that he used a bad example of one. As for that other blog, to be polite it doesn't exactly come off as being an objective analysis, certainly not with all the hyperbole it contains.

My own impression of the SF is that it's a very competent ultra-portable with an action that could be described as being on the stiff rather than light side. I have actually travelled with one and found it to be well suited to the role. Is it the best ultra-portable ever made? No. But it's certainly up there in terms of build quality and it doesn't deserve to be panned. I would definitely pick one to type with over a Lettera, mostly for the reason that Janet already pointed out: there's something amiss with the keyboard on the Olivetti models that make it easy - for me - to miss keys. 

You have to take some reviews with a grain of salt, after all they are based on a machine that is at 40 years old, and some, as you would expect, work better than others because they are in better condition. You also have to factor in a person's experience with typewriters. A reviewer who owns 10 machines will not have the same comparitive base as someone who owns 100. And until you've tried most of the other models that were available at the time, how can you provide an objective "review" of a particular model's performance? Never forget that the internet is the world's greatest source of misinformation...

I am very fond of my 1940s Hermes Baby. Although it does have the occasional hiccup -- the carriage jumps a bit from time to time -- I love the key action. I think it crams everything into a small space but still feels the same as typing on a larger portable. 

[Purely a style quibble: I don't like any of the later Hermes machines, even though they seem almost universally loved, because I can't get past that horrid seafoam green color. Sometimes it's the little stupid things that make you turn away from a brand.]
 

Oh I'm a big fan of pretty colors for my typewriters. And I agree that those 20s-30s Royals with the colors are wonderful -- I have a red one and a green one, and now I'm dying for a blue one. But look at this one Tom Furrier had in his shop -- that's insane! I couldn't concentrate typing on a machine like that.