Yes ignore ambient lighting. You should always switch that off. Have a look at the Xrite ColorMunki display as well. If you do any of your own printing, the ColorMunki Photo is worth the extra investment as well.
I personally use the i1 display pro which is the pro version of the ColorMunki display.
Any of these will do a good job. Avoid the ColorMunki smile or Spyder 4 express as they are both entry level colormeters and not worth it IMO.
+1 for Xrite's ColorMunki Photo. Works very well. Right now, any printing is from various online and local shops so I just need the monitor calibration, but I hope to start taking on some printing in home this year and the product will help calibrate the printer as well. Since you don't plan on printing, definitely consider ColorMunki Display.