Heya,IMAGE LINK: https://flic.kr/p/mNPeQj DPP_1802
I handhold my 150-600 Tamron a lot. I find it not to be that bad. I only use a tripod when I'm trying to land a very far away shot, or in poor lighting where it's hard to get focus so that I can manually tweak if necessary. I get fatigued faster holding my macro setup, than hand holding the 600mm on a gripped dSLR, and I'm no hulk. It's really not that bad, it's a light lens compared to other telephotos.
As for quality, the 100-400 versus 150-600 always comes up. There's always commentary for and against each one. After playing around with telephotos, I stayed with the 150-600 because frankly, getting the quality you can at 600mm, even on a lowly APS-C sensor, is simply better than 400mm on APS-C or full frame in my book. Shooting at 600mm does take a learning curve, but it's not a big one. It's mainly understanding how vastly important fast shutter speeds are, and tracking a moving target, as those two things are a new world of difference compared to 400mm and 200mm. I can track an osprey at 400mm like it's crawling. But at 600mm, it's a challenge.
Anyhow, here's some examples of the Tamron's quality at 600mm on a lowly 650D's sensor, where a 400mm simply cannot fill the frame's pixels. You be the judge. Again, this is with junk equipment even, not a nice camera, so imagine if you were pushing around with the fabled 7D2, 1D series, etc.
, on FlickrIMAGE LINK: https://flic.kr/p/npRAZw IMG_0925
, on FlickrIMAGE LINK: https://flic.kr/p/npdm8o IMG_3484
, on FlickrIMAGE LINK: https://flic.kr/p/nzuqMS IMG_5085
, on Flickr
What I've learned from shooting at 600mm, is that no matter what camera it is, it's probably good enough for good images. But you definitely feel it, when shooting 600mm and wildlife, when ISO is limited and when ISO is not higher quality. I'm holding out for a future APS-C with higher ISO ability and extremely clear ISO 1600 quality basically. So it'll be another generation, past the 70D, before that really happens. The 7D2 hopefully has something like that. But that's my biggest want for an APS-C is the ISO performance and range to start going up. I can land focus even with a junk rebel, so I'm not concerned with having super duper AF performance of the 7D. I'm more interested in higher ISO, so achieve the fastest shutter speeds. That alone helps the most, at least, in my experience.