Last week Avi (my team leader) and I were in a meeting with Systematics the representatives of ESRI in Israel.
We ought to ask some questions about the GIS Server, and I will bring here some of the answers we've got:

1. The GIS Server 9.1 won't work with the SDE 8.3
2. The ADF(Application Development Framework) for .Net will help us to develop GIS applications more productively (using my favorite drag&drop action).
3. While the ADF is very useful it is also very simple, most of the wanted features you would have to program by yourself, such as saving the maps history, calculate the distance between two (or more) points which are not in the same extent. (those two examples were implemented in our systems today and won't be provided in the ADF Controls functionality)
4. The ADF.Net won't work with the .NET2.0, we should wait for the next release.
5. The GIS Server based on the ArcObject model, which give you more functionality (the same as we have in the client) such as editing.
   No more activeXConnector problems.
6. The performance in the GIS Server is not better than the ArcIms, which are both very slow (you can see it in the examples below)

Here are some demonstrations of the products:

• An example of caching your maps,
  I loved the idea of using the cached maps (My Maps) on the right.
• Simple example of tool tips on map (this one is damn slow, while we have only 4 layers).

   Those two still suffer from the known issues of bad performance, 
   even when they are only small projects.

• Another useful examples http://caromap.esri.com/.
• The next example is from Nikhil, I am not sure if he uses the ESRI Technology but this one is my favorite: http://www.nikhilk.net/Prototypes/PhotoMap .