I took the new AT&T modem (KK, 4.4.2) UCUCNE5 for spinÖ and here is my experience. Attached screenshot are the results from a quick and dirty modem speed test (using SpeedTest.NET). Iím currently running a 4.3 rom (SkyNote Vanilla MK6 base) with the UCUBMK6 modem. Just prior to upgrading my modem to the new UCUCNE5, I ran speed tests on my current modem (UCUBMK6)... then flashed the NE5 modem, and re-ran tests (same local server, immediately after flashing new radio). Results will obviously vary depending on your personal situation (geographic location, phone setup, etc); however for me (NorCal area) the KK NE5 modem improved my mobile (LTE) download speeds (20%) and mobile (LTE) upload speeds (19%)... and improved my WiFi download speeds (24%) and WiFi upload speeds (7%). I ran 2 simple tests each on WiFi and same 2 tests each on mobile LTE (on both modems)... then averaged the results. Take it for what it's worth (again, you need to test in your geographic location), but for me, appears the KK NE5 modem improved my speeds even running the 4.3 MK6 rom. As soon as I upgrade rom to 4.4.2, Iíll re-run tests and post.
Also... was on the road for past 3 hrs and constantly tested mobile reception... held on to LTE signal 100% of time (no signal drops or degradation).. rock solid.
Thanks to Zen Arcade for pulling the UCUCNE5 modem.bin and packaging it in a flashable zip: