I have a different Johnson Controls unit with a nice thin capillary wire to the probe, it just goes under the seal. On that one you're looking at, you'll probably need a hole, or to collar your freezer.
Do you see a strong need for digital displays and stuff? Cuz the $45 basic Johnson Controls unit I have works great.
I would go with more than 5 feet. I have 6 feet of beer line and I get too hard of a pour at my carbonation psi...and its no fun to have to dial down and vent every night to pour a beer. I plan to put 8 feet on when I change my lines in the future.
most people use a keezer for lagers, not ales (unless they are stuck in the desert)
Primary: English Mild
On tap: Pale Ale, Lancelot's Wheat, English Brown Ale, Steam Beer, HoovNuts IPA
Bottled: MOAM, Braggot, Raspberry Melomel, Merlot, Apfelwein, Pyment, Sweet mead, Cabernet
Gal in 2009: 27, Gal in 2010: 34, Gal in 2011: 13, Gal in 2012: 10