Using COLL for Fridrich is rather a waste, in my opinion. The concept is solid, but you will take too much time learning cases that rarely appear. For pure Fridrich, maximizing your OLL and PLL potential is far more important than complicating your LL.
However, with EO methods, COLL becomes the logical next step to the (current) Holy Grail of speedcubing - ZBLL. Though I have found the VH system to be slower than plain Fridrich, COLL is a great stepping stone to ZBLL. Also, COLL gets your EPLLs down to sub-2 when all your other PLLs are hovering around 3 or 4 seconds.
I have mixed feelings about COLL, despite the fact that I am using VH as my main method as I move on to ZBLL.
For the record, my best time with COLL was X-Cross + F2L + EO skip + a Pi COLL + EPLL skip = 17.37.
My best time was on this scramble: B F L2 F' L' B' F2 L2 B' F2 L' R B D2 F2 D B' L R2 B R U2 D2 L R2 where I had Double X-Cross + F2L + f' L' U' L U f + Y permutation = 15.31. Later I tried this scramble with VH and got a 20 ish solve.
Though I love VH (well, the COLL part), I have to say that learning pure Fridrich is a very acceptable way to get faster at cubing. If you want to learn COLL, go for it!
Here are my algs, if you guys want (and some cheesy bit about recognition at the bottom):
http://nomiswanson.fileave.com/COLL.Algorithms.pdf