OK, so today i went and bought a real tripod, ballhead and quick release clip...Manfrotto 724B and 3299 Plate. this was based on my need for something suitable for travel. it's light but still has good stability and plenty of height adjustment. comes with a nice bag also.

i did some test shots and used the mirror lock-up function with the self timer. this provides for a 2 second delay after shutter button depression...enough for any minor shake to disappear. also eliminates any inference mirror movement might have on image sharpness.

this shot was with AF on and IS off. focus point is the middle of the chimney. exif below:

Aperture-Priority AE
Tv( Shutter Speed ) 1/100
Av( Aperture Value ) 16.0
Metering Mode Evaluative Metering
Exposure Compensation 0
ISO Speed 200
Lens 70.0 - 300.0mm
Focal Length 300.0mm
Image Size 3456x2304
Image Quality Fine

here's the shot, full frame, resized to 800 pixels wide. not bad:
<img src="http://marsavius.net/photography/images/70-300_tests/Img_1883@300mm-resized-to-800.jpg">

here's a crop at 100%:
<img src="http://marsavius.net/photography/images/70-300_tests/Img_1883@300mm-crop.jpg">

so this to me looks like it's a bit soft. but when pictures are re-sized for normal viewing this lens will be quite fine i guess.

if you can think of anything different to try please comment.

Say - 5.6, 8, 11, 16? It does look a tad soft, but nothing a little USM shouldn't be able to take care of. Is it worse in portrait mode?

Does that tripod have hard tips of metal not rubber? Tripod needs stiff ground like rock or some weight.
Mirror-up shoot option may help to reduce movement due to mirror shock.


<img src="http://i7.photobucket.com/albums/y298/nogarohiro/051204side-100crop.jpg">

This is 100% crop of the pic added below.
Vertical lines on the headlight lens are visible, but horizontal lines of the reflector are not.
I took this with Tamron 28-300mm zoom, obviously less resolutive lens than Canon 70-300mm IS.
I set my camera on a tripod with metal tips on hard pavement, and exposure was 6 seconds.


<img src="http://i7.photobucket.com/albums/y298/nogarohiro/sidesmall.jpg">

At f16, I doubt it's a front focus or back focus issue judging by the pic...but try it anyway. Nothing to lose.

Short of that, I would document the issues, and sent this lens back to canon for repair. Even 100% crops should look better than this.

Also have you done a focus test with that sheet of paper yet? I don't remember my Sigma 70-300mm being that soft and that was a $165 lens. I did sell it because at 300mm I could never get the shutter for a sharp shot...shaky hands.