Last summer I installed a Highway Dirt Bikes (HDB) kit on my WR250R. Also a ProTaper Henry Reed handlebar, G2 throttle tamer, and Oxford heated grips. Here's a few observations:
The HDB kit is solid. I did the NexGen, with HDB being nice enough to exchange the regular kit for the NexGen - the Ultimate Handguard kit was a little difficult to install due to needing to bend the guards. Fits great, very solid. I also installed 2.125 (2 and 1/8 inch) lower clamps. These allow the top-plate to fit without causing interference with the key. With the Henry Reed Pro Taper bar, this setup gives me a very neutral position - my elbows are bent roughly 90 degrees when sitting. For reference, I'm a shade over 6 feet and have a 33 inch inseam. I can stand comfortably now.
The Oxford grips work great. Slightly wider diameter feels better than stock. Heating is nice. Hooked up with Eastern Beaver 3CS.
G2 throttle tamer - I was getting a lot of snatch in the throttle - not related to clutch control. The G2 combined with the Oxford grips make for a fairly smooth engagement. There's just a nice amount of snatch and with a little clutch control, slow speeds are much easier to manage. Not silky smooth, but nice. I speculate that the G2 with the wider Oxford grips balance out differently than just going with stock grips on the G2. I'm a fan.
I hope this is helpful for others. Happy to answer questions as they come up.
MadYam
2015 WR250R