Actually, the thing with springs, or ANY mechanical-basis verb, is that is has LOTS of character. Which can work well now, but you don't want to have to rely on them as your main source of reverb.
Ah, my very first session, we had both Sound Workshops spring unit and an Ursa Major (I know people love them, but not that good really). Instead, I set up two mics in a nearby stairwell as chamber and got stereo reverb that was 10x better than the project itself...
I still use the Sound Workshops now and then... but I modded it.