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.