I'm not a fan of the Sideshow style body, but the build quality and plastics are much better than the no-name $20 bodies on eBay. One of the bigger issues for me is that Sideshow traditionally hasn't had enough variety in their body sizes to accommodate different characters. WRT to posing, the shoulder are what I find most restrictive and really hurt the appearance of the arm length when raised.
I've not had any of the issues bending knees nor torso to get him into a suitable riding position, even on the Hasbro Bike with absolutely does not have a 1/6 seat (it's way too wide).
They've developed at least one new body which is premiering with the new Luke figure - I don't know what's different about it.