Our user environment is, and is likely to remain, 8.5.3. There is a possibility we’ll be doing a server upgrade to 9.0.1 so I know I need to install and use the 9.0.1 admin client. I believe this also pushes me to the 9.0.1 designer client as well.
I’ve checked out the ‘what’s new’ for 9.0.1 designer and don’t see anything that looks like I could do with the designer that would break apps running in an 8.5.3 client. We don’t do html, xpages, java, or javascript; just LS and Function language.
It looks like I’d be safe doing design work with a 9.0.1 designer but wanted to bounce it off the group just to make sure.
I’ve been using the 9.0.1 designer to build applications for a mixed 9.0.1/8.5.3 client population for a while. There are some features available in designer that won’t work in the 8.5.3 client (for example, a different way of grouping view entries by date), but as long as you avoid those new features I’ve had no problem building apps for 8.5.3