TFF pretty much covered it in regards to GEC's lines of slippies. For my own $.02 I will add they are some of the best quality production slipjoints out there. I own many of them, most of mine are actual GEC brand but I do have some Northfields and Tidioutes. As TFF also mentioned a good majority of their patterns have very strong backsprings, something to keep in mind. They have a tendency to make some nail-breakers, but like TFF I too like them like that.
Also, they are not known for razor sharp edges. While their quality of materials and fit and finish are usually exceptional they tend to put mediocre edges on their knives. Sharp enough for general use but often times not up to par for most people. Their edges are their one down side in some regards......but outside that you'd be hard pressed to find much better in a production slippie.
Here's my current collection of them thus far.............
And here's a few more I have added since the above pics were taken................
I have one more I haven't got pics taken of yet as well, a Tidioute #73 linerlock in Rosewood that was a gift from a friend. I need to get some pics taken of it soon. Oh, I did forget to mention one other downside to them.......they are addictive!