Good acting, plot, not much of a mystery. The entire movie rested on action and special effects, both of which were done well. Robert Downey Jr plays a decent functioning whack job and Jude Law plays a excellent Watson.
I had hoped for more snappy banter between the two. It had it moments, but not a lot of spark there. Their acting did bridge their Watson/Holmes friendship rather well. There was okay dialogue when Holmes and Watson talked to other people, just not to each other.
Excellent Steam Punk feel all around. I felt they were in the 19th century.
Holmes' adversarial love interest should have had a few more years beneath her. She looked way too young to be what she was. P'raps that's just me getting old.