I personally have the VE-100 wich is just an on/off thermostat but it's already failed me once on a single rack (Temp got to 120) . Stuff breaks, thats life but when it happens to you personally it'll make you think twice about going with a particular unit a second time around.

The specs on the VE-300 look great though, but the specs on the Herpstat and Helix units look great too as does the track record.

Just my 2 cents worth