The mk I Canon 24-70 f/2.8 was one of the softest and worst of the 24-70 I have ever used. Anything else is an upgrade. Just go get the tamron and enjoy. If you need more info, go read the reviews, test and decide for yourself.
You can try the Tamron 24-70 VC if the Canon 24 70 is too expensive for you.
For the record the Tamron 1 is good and popular. But whether it suits you or not. Nobody can help you. As it is or can be very subjective.
if i were u, i would definitely save up slowly and get the 24-70 f2.8 version ii. i might have to wait, and it might take months, but i know what i get is the best & i would definitely enjoy it the most & without having to constantly think "if only i had saved and waited to get the canon version ii instead..." besides, i guess this is a hobby and not rice bowl for u, so its ok to wait a while... in the meantime, learn more and maximise whatever u have first..
can not afford than just get whatever is within your budget,
if you are a pros, this will be your tool of your trade, you will some how find the money some way some day, don't have to think so hard now, surviving first, expending later.
if this is just a hobby, than why make yourself so miserable? you are suppose to enjoy the hobby, ask yourself if without a pro grade lens, would it make your hobby less enjoyable? w
Am a fortunate owner of a not as bad as many people say 2470mkI. While its not as sharp as my 70200mkII, it does get the job done and is way cheaper than the 2470mkII.
Of cos having upgraded to the mkII, I now know why people say its worth saving and "eating grass" for.
If that is way out of your budget, I would suggest a 2nd hand 2470mkI but remember to test a few copies and look for UZ code first. Both mine and my friend's one were not as soft as most people say it is. wonder if Canon knowing their mkII will take sometime to release did something to the mkI.
If you don't wanna take the risk or don't have the time to slowly hunt for a good UZ 2470mkI, I would suggest the new Tamron 2470 VC. While its slightly sharper than my old 2470mkI, unless you print or export huge photos, you cant really tell the difference out of Lightroom/Aperture/etc unless again you are the type who uses out of camera jpeg. But some say the VC is another reason why the Tamron makes more sense.
Ultimately just make sure you will enjoy the lens.