I have to say though that the most recent upgrade that has had the biggest effect on my brewing is converting my chest freezer in to a lager fermentation vessel. I can now ferment 4 lagers at a time which is awesome.....
How do you ensure that each lager is at the right fermentation temp? I have a chest freezer and johnson controller, but if I insulate the probe and tape to the outside of one fermenter, the compressor kicks on if the yeast starts getting too aggressive until the FERMENTER temp gets down...thus while I have room for two, my Johnson (heh) is only able to monitor the temp of one.
I'll bring the newly brewed lager just below the fermentation temperature in the chest freezer using an IC and then ice bath. I typically ferment all my lagers at 50-52F so I'll bring the new one to 45F, pitch 45F yeast and let it rise to 50F in the chest freezer. I have a separate fridge for lagering so it works quite well.
As for the probe, I have it in air, not taped to the fermenter. You need to account for 1-2 degrees but it is manageable.