I’ve been using VS 2003 since I upgraded from 2002, and I’ve been using VS 2005 Beta 1 for about a month, and I’d like to share my experiences. I have them installed side-by-side on my laptop, and they play fine together, but when I installed 2005, the v2.0 ASP took over my IIS apps, so I had to run aspnet_regiis to set it back to v1.1. This problem is solved with 2005 because it doesn’t need IIS, and I don’t use IIS with it. When you run a web site in 2005, it starts a built-in webserver that runs on a random high port for just as long as you need it too. This is independent of IIS. Because of the dynamic compilation model of code-beside, I don’t have to rebuild every time I modify page code. That’s nice. VS 2005 Beta 1 has some performance bugs in its build process, however. It’s a bit slow compared to 2003, but it’ll get better. I never realized how spoiled I was with 2003 since it builds so fast (of course this should be expected). 2005 will get there, but for now I have to wait for every build. Also with my 2003 web apps, every time I rebuild, I have to wait a while for the web app to recompile and serve up the page again. With v2.0 Beta 1 this restart/recompile process seems to be improved because the wait isn’t as long.
Bottom line: VS 2003 and VS 2005 work well running side-by-side, and I even reference an assembly build in 2003 with 2005 (proof of version interoperability). I have version 2 classes that inherit from v1.1 classes. Seamless.