After using IntelliJ for the last nine months or so I have realised how much Visual Studio sucks (even with Resharper). The problem I have with VS is the IDE seems to be focused on everything but writing code and I feel there is only ten percent of it I use and that only does ten percent of what I can do with IntelliJ. I, like many others, really wish there was an IntelliJ plugin for .NET (in particular C#) or even a whole IntelliC, however the news on the street is despite JetBrains hinting rather explicitly that such a thing was in the pipe line they've shelved the idea (BOOO).
I can't blame JetBrains for wanting to focus their efforts on Resharper: MS developers, as a herd, generally keep to the MS straight and narrow and fear wandering from the vendor's path of least wisdom. It makes no commercial sence to develop an alternative IDE from Visual Studio when most MS devs won't even bother to look beyond the MS brochure. As a plugin Resharper is going to hit a bigger market.
This is a shame and a loss for choice: the Java community has healthy competition with its IDEs and plenty of innovation with it but, Borland aside, this culture doesn't exist in the mainstream MS world (hence why Visual Studio's 'refactoring' and 'testing' features are a joke).
The other issue is that Visual Studio only runs on one platform (Windows) for one vendor (MS funnily enough); from the ground up most Java IDEs support multiple platforms and multiple vendors of the JDK and compilers. Why is this of any relevance for .NET - who would want to develop it on anything else when it only runs on Windows anyway? Firstly I don't want to develop on Windows: I find it an awful OS for doing development on and I am far more productive on Linux or OSX (like many I have a preference for a different OS which happens not to be Windows: why should that even be a statement?), secondly I don't necessarily want to run my .NET applications on Windows: after the luxury of working with true multi platform languages such as Java and Ruby I find it really frustrating to have to ditch everything positive about working cross-platform (and that means working on Windows too) and be shoved into a corner where my choice is simply XP or one of the 26 variations of Vista.
Even though I may not express a preference for working on Windows or with Visual Studio but there are many things about .NET I really like: there are things about the cleanliness of the language and the SDK which trumps Java (generics anyone?). The real advantage Java has over .NET is the community around it and the way Sun has left people free to contribute to it, there is far more innovation coming from the Java community than from the .NET one (hell, the .NET community is just trying to port as many Java projects as quickly as it can). However the .NET community is growing (especially with the ALT.NET movement) and it isn't to hard to wriggle out of the MS straight jacket. All in all there's a real feeling of excitement around .NET at the moment despite MS's attempts to lump as many bad practices into it as they can. As a result .NET is a serious contender to Java except it falls flat on its face when it comes to cross platform support.
Well there may be some hope out there: mono is coming along nicely (with almost full 2.0 compatibility) and comes as part of Gnome (so for Linux it's already there) and there is a version for OSX. With a bit of support and real world proof mono has the potential to become a real Java killer.
The problem is you're not going to be able to compile to mono in Visual Studio and even if you could you can still only run VS on Windows solving only half the problem. The other problem is Mono IDEs suck: monodevelop, a sterling effort, is like going back in time 15 years. SharpDevelop (from which monodevelop was originally forked) would be cool but again it only runs on Windows (booooo to you icsharp).
A bit of research and I stumbled across a little IDE from Omniture call X-Develop. Not only does it run on Windows, OSX and Linux but it can handle C#, J#, Visual Basic and Java compiling to whatever framework you choose including mono. The word on the blogoshpere is that X-Develop is a usable, productive UI and despite not being as feature rich as IntelliJ (it's refactoring support is weaker) or Visual Studio (UI designers) is a slick, quick, lightweight, cross platform IDE, which includes all the essentials including basic refactoring (one up on VS), error highlighting (another up on VS) , debugging etc. The good news for fans of other IDEs is that you can choose to map keybingins from Visual Studio, IntelliJ, Eclipse and others.
The downside is you have to pay for it and at $499 per license it isn't the sort of thing you'd buy on a whim. Naturally I'd prefer it to be open source but I'm going to be realistic that people have to make money though a cut down OS version without the designers etc. for free may be a wise move to get people hooked. Omniture seem to be giving a serious proposition that no other vendor can match in terms of true cross platform, cross framework development and that is a fantastic thing.
The problem Ominiture are going to have is appealing to the Java and Linux community who do have a preference for free software. The problem mono has is that without a decent cross platform IDE it's not going to gain serious ground. I think both sides need to reach out and touch each other to ensure mono gets the real-estate it deserves. I for one would be seriously excited about developing true cross platform applications in C# on my Mac or Ubuntu. Hopefully it may be a future arriving quite soon and not just another broken pipe dream.