See Steve Stafford's Revit OpEd Blog post:
Revit OpEd: Tekla BIMsight - Free divided by Free is still Free!
Another item that came from attending BIMForum Winter 2011, Tekla BIMsight. I admit that my first reaction to hearing the name was, "Oh, a cloud sharing/viewing solution?" Then I saw the spelling of the name.
Using price alone, if we compare Autodesk's Navisworks Manage and Tekla BIMsight:
Navisworks Manage: $10k-ish (USD) $1.5k yearly subscription
Tekla BIMsight: $0.0k (USD) aka FREE (no subscription)
Quick Comparison between Tekla BIMsight and Autodesk Navisworks:
Want to know more about Tekla BIMsight?
Go check it out here!