Well, I have been reading a lot, a lot, a lot about .NET and SharePoint. What to do? We are trying to get into the government Gebiz SI contract… and all the contracts there are basically tilted towards the .NET platform. Dun learn also cannot…
But having said that, I think .NET is a superior platform for SI based development.
Superior Tag Libraries (in Java Speak)
It is kind of like JSP tag libraries. Only different thing is… It has a defacto set of super powerful tag libraries that everybody uses… part of the Windows Web Forms. Conversely, java has too many small sets of tag libraries… and none of it really that powerful.
Integration to IDE
On top of that, .NET Visual Studio is a first class IDE. All those amazing tag libs can be dragged and dropped like components into your web form! I remember reading about JSP Tag Libraries some years back.. they were supposed to function like that… but till now.. not sure if the integration is already there… maybe Chuen Yang will know… 
Database Integration
.NET somehow can work for dummies. I guess… they like to have a very easy drag and click platform such that even for SQL statements, it can be literally dragged and dropped out. What I like about it is the tight integration. You can actually preview the data in your control while in development mode! Wow… but frankly.. for the rest of it, i.e. the automated way of writing sql.. I can kind of do without. I am more familiar with SQL than .NETs drag and click way of generating the query…
DAOs and Business Logic Layers
Well, .NET also has DAOs and Business Logic Layers… Difference is … once again.. the DAO’s can be be dragged and clicked….
All these.. makes writing customised application blazingly first…
Haha… your friend here is outdated with Java tag libraries. I’m more inclined towards GWT