Darn it! I just did that yesterday. I thought I read in the app info that it would work with previous versions. If I try one to check will it bork my phone?
I have some saved from the new app and some from the older one.
Edit: actually I only updated rom manager. The cwr version is the same so I assume I'm ok?
Well, the worst that could happen is your restore job just fails (which has happened to me for this reason), and you have to start over again.
Updating ROM Manger is different than updating CWR. CWR updates are done THROUGH ROM Manager. And even if you do need to go back to an older version of CWR, you can do that through ROM Manager.
If you're not sure, why not just make a nandroid now?
Now, this is just my own personal opinion, but here goes... Nandroid backups are FULL IMAGE backups. That means that they are great for creating "checkpoints" that can be used to easily revert back when testing ROMs, kernels, mods, etc. However, because they contain all your apps and data based on a particular snapshot in time, these nandroid images also grow "stale" very quickly.
I generally make a nandroid about once every two weeks, even if I'm not planning on making any modifications to my phone. Why? Because I also delete any nandroid older than about 2 weeks. After about that time, the data and the app versions contained on the image are outdated enough that it would almost make more sense to just start from scratch.
Seriously, If you *really* wanted to go back to an old version of Froyo you ran months ago, you'd have a much easier time installing the ROM from scratch and restoring saved data from your current ROM than you would actually restoring a nandroid from that long ago. Trust me. If you nandoid is older than a few weeks, you might as well just delete it...it's never going to be worth going back to.