I've got one of the digital controllers from Williams Homebrewing and I like it.
I use it to turn a chest freezer into a keg cooler.
As far as lager goes, I'm fairly new. Last season was my first real attempt. I took advantage of my basement being in the low 50s during the winter. At the moment I have two kegged lagers in said chest freezer maturing at 32 degrees. I must say the changes this brew is going through as it ages are amazing.
That means my ale must be dispensed at 32 as well. Oh well. Purists be damned. Cold beer is nice.
I've never used my controller to maintain fermentation temperature.
I do ale when it is too warm for lager, and I'll be doing lager from now on when my basement is cool enough.
Cheers!