Dylan, your comments are based on your own, personal, biased, limited, non-scientific experience with one copy on of one lens and one copy of the other.
Now, nobody denies that it is enough for you - or even better, that this is the most important review to you.
That said, all the main in-depth reviews agree on the value of this lens and on its superiority to Canon Mk1. It goes by itself that if someone was happy with the Mk1, he will be only happier with more sharpness and IS at a very good price.
Is it better than Canon Mk2? Optically and mechanically quite likely not, but it has IS, and many people like this feature a lot. Also, it costs a half, and even more people like this feature.
So please stop this pointless crusade and try to understand that better can mean a lot of things, and ultimately it means "it suits my needs better".
'Testing' one copy of a lens that hasn't been calibrated with something like FoCal to your camera body in a shop means absolutely nothing in an objective sense.
Also IS is helpful, but IS has not been around forever. People have been shooting without it for a looooong time.
Anyway ye useful, but a deal breaker? For a pro no... You will always shoot in a range that will produce a sharp images. Although I will admit IS does help with creativity, shooting in lower light, but with better high ISO camera performance you can rely less on IS. Also the subject is more of a concern than camera shake, if you are an experienced photographer you know the limits you shoot in, its also down to technique.
People took photos for a long time before autofocus was around (and still do using their zeiss/nikon ai/leica glass on ef cameras). That doesn't mean that AF is useless to professionals.
For certain types of video (particularly run and gun documentary/documentation/wedding reception footage), IS is a massive plus to the point of quite possibly being a deal breaker (and this is where you're likely to be using a standard zoom quite heavily - for fiction where you have controlled conditions and time to set things up then you're likely to be using primes). Or do people making money from video count as amateurs now?
My final comment on this topic:
@ Syder -- I'm 90% sure you haven't own the Tamrom nor Canon ver II yet, therefore, your comments on these lenses are pointless. A quick advice for you, don't give comment on the lenses that you haven't own.
I own Reikan FoCal Pro version. All my lenses 50L, 16-35 II, 24-70 II and 70-200 f2.8 IS II are succesfully calibrated(AFMA) with FoCal. And yes....that includes the Tamron - W+1, +2T @ f2.8
Just for the record, I'm not a Canon fan. If I in the market for the 35mm prime, the new Sigma will be my choice.
Let close this chapter and move on......