I think a looper is a worthwhile tool in some cases, but not all. I really just depends on what kind of signal chain you have, ie what's in the chain, how many pedals, the types of pedals and the overall length of patch cord you have to use to route all of that.
A good buffer at the end of your chain will go a long way towards preserving your tone. It will negate signal loss due to lengthy cable runs. A lot of people just put a Boss pedal at the end of their chain. Even when off, the signal is buffered. I actually use the tuner one, and leave it on.
However, this won't make a difference if you have a non-true bypass effect in your chain that is noisy. I recently picked up an RE-20 from dcountry13 over at BYOC. It's a terrific sounding delay, but it is noisy as hell when off. I mean, super noisy. So, for that one I would probably build a single looper to switch it in and out of the chain.
Or, you could break your chain down into a couple of groups and do a smaller looper to turn on multiple effects at the same time. Like, an OD path, and modulation path, a delay path and so on.
If you want to get REALLY fancy, you could experiment with using a looper with some blending circuitry to put effects in PARALLEL with your signal chain. So, maybe putting your chorus in parallel with a blended dirt and clean signal. Once you open that door, the possibilities are endless!