Patentees rarely win.  “By far the most dramatic finding of our study is that patentees rarely win doctrine of equivalents cases. Overall, patentees won only 24% of the doctrine of equivalents cases decided in the last eight years. Compared to the overall patentee win rates on other issues -- 54% on validity alone in cases at various stages of litigation, (51) and 58% overall in cases that make it to trial (52) -- and the baseline assumption in the economics literature that plaintiffs should win about 50% of the time, (53) this is a remarkably small win rate for patentees.” (John R. Allison and Mark A. Lemley, “The (unnoticed) demise of the doctrine of equivalents,” Stanford Law Review, February 1, 2007)  Peruse more books by John R. Allison and Mark A. Lemley.

Everybody’s a loser in patent infringement knock-off litigation cases.  "But I will say this much.  Everybody's a loser in these kinds of cases. You never get total damages, and often you don't even get legal fees. But if you don't fight, you lose your patent. So what's your choice?"  (Tomima Edmark, Dallas inventor of the "The TopsyTail, Patent No. 5,036,870, quoted in Rusty Cawley, “Patent Protection,” Dallas Business Journal, June 12, 1998)