on start up i see a small delay in the UI the first time i load 2010 and after that i do not see a problem with ui speed.
i do see a few times where the screen needed to redraw and if i re-size the app it snaps up the right update, like opening a code or design window on some occasions it does not show the new edit window.
the help / doc engine yeah that one i *TOTALLY HATE* what they did, to me it was a HUGE step in the wrong direction. IMHO they should just say "For Help open a GOOGLE and search there ...." that's what i think of the new help system.
script debug - i have never really used VS to try and debug any JS so i have no feedback there.
Multi-Targeting I have not seen any issues with .net 2.xx 3.xx and 4.xx i have several apps that are in each version and for me this works fine.
I do not like the following:
1) lack of support for my Vs 2008 smart device projects.
2) SQL RS Editing - why not have the ability to edit a RS 2005 report and an RS 2008 report with VS 2010
if they fixed the two missing items I could uninstall VS 2005 and VS 2008 of all the machines i use!
so over all for me the new Support for SIlverlight and WPF and the ability to work on 2.0 and 3.5 and 4.0 apps
plus a lot of other stuff they have done make it a no-brainer to keep 2010
I just put out a V1.0 of a new app for a customer in WPF and they love how it looks and works, they have already requested a new version with more features.
I see over the next year the start of a shift away from WinForms appps to a mix of WPF and SIlverlight for our core clients.
I am starting to track how many desktops have what version of .net and planning how i can get 4.0 on them w/o a big manpower issue.
they do not have an AD system if they did i would setup an auto update process.