i've used arccos for over 2 years now and i love it. i have the sensors that screw into the grips, but next time i regrip my clubs i am getting the built in models.
the insights it gives you on your true distance on every club is the most valuable for me. like most golfers, i thought i hit it further than i actually do because i used to calculate by "if i hit this 7 iron exactly perfect, i can hit it this far.." now, i have the data that shows me that on average, i hit a 7 iron an exact distance. my GIR's have went way up and when i miss a green it's by a lot less.
also, the caddie function is really solid. when you have enough data in the system it starts recommending not only what club to hit, but recommended strategy on a hole that gives you the odds of making the best score. cool stuff.
it keeps getting better and better with enhancements as well. customer support from arccos is also really solid.
hope this helps.