I installed my 13T front sprocket today and went for a test ride. I love it! The 13T spreads out the power band from the 14T's very narrow 5000-7500 RPM, to a very usable 3500-8000 RPM.
On the low end, I have power in 1st gear at 3500 RPM, instead of at 5000-5500 RPM with the 14T. This will really help starting out on hills and on trails. I was even able to start in 2nd gear, which would stall the engine before.
On the top end in 6th gear, I saw 5500 RPM at 50 mph, 7000 RPM at 60 mph, and 8000 RPM at 70 mph. I still had throttle left at 70, but would probably downshifted to go faster.
I didn't try it tonight, but with redline at 9000 RPM, 75 mph should be easy and 80+ should be doable. This test was up a mild incline, but certainly not a steep mountain pass. I will be testing that by this weekend
I don't think I lost any top end with the 13T. With the 14T, I usually found myself cruising at 65 in 4th gear. I almost never used 6th because it had no power. But with the extended power band from the 13T, all the gears are more useful.