Nope, you don't need CWR, unless you want to trt flashing other roms, or some "hotfixes" that are flashed through clockwork, or if you want to do backups of your currently setup Nook Color (the biggest reason to do backups is IF you install CWR to start messing around with other ROMS).
If you want to do some backups of apps etc. but not a "complete" backup, you can use the Titanium backup app w/o needing CWR.
Also, one caution and further reason to avoid CWR unless you really want to start getting your hands dirty: there are numerous reports that CWR when flashed AFTER an update to 1.1 (rather than before the 1.1 update) CAN cause endless bootloops into CWR (it happened to me so I followed some of the other reports.) Supposedly a reboot after flashing CWR but before booting into CWR will prevent this, but I haven't tried it to see.