3 years ago today, ArcGIS Engine first shipped as part of the larger ArcGIS 9.0 release. It's hard to believe it been three years already but at the same time 9.0 seems long ago. The 9.1 and 9.2 were solid updates for Engine and more improvements are on the way with 9.3 which is currently under development.
There are many successful deployments of custom solutions out there based on the the ArcGIS Engine Runtime and many more to come. Thanks to all the ESRI staff who have worked for many years on making ArcGS Engine what it is today.