have pretty much for the last 3-4 years used coretemp started using it as a widget on win 7 but now use the full version. I've found it to be pretty reliable. Use hardware monitor as well, and its good but I like the tray icon that coretemp give me lol.
Personally prefer Open Hardware Monitor with the +15C threshold to get the correct AMD CPU temp, also use custom rainmeter skin for my display outputs.