Make sure you have a very accurate temperature controller. You absolutely need to be able to maintain the exact temperature, and it needs to be calibrated. If your home-build is off by even 2-3 degrees, you will not get good results, and on some things, like low-temperature chicken breasts, you could even get into safety issues (cooking at too low a temp).
Don't get me wrong, I am all for the home-build approach and, for my very occasional sous vide meals, I too rely on a home-build (a crock pot that is controlled by a temperature controller of my own design). I used a Thermapen to calibrate it, and that Thermapen has itself been calibrated, traceable to the National Bureau of Standards. That last sentence may seem like overkill, but as someone who got his start at one of Hewlett-Packard's test and measurement divisions, I can tell you that it is actually incredibly important to know that 140 degrees is really 140 degrees and not 135 or 145, and the only way you know that is by having a device that has been calibrated by a reference standard that can trace its calibration back to the reference standard maintained by NBS.