Don't have the skills to do a good Karhu G write up, but i can share with my fellow ghostbears how I use it to good success!
"Hey diddle diddle, straight up the middle!" The Karhu G can run 10 hexs straight, that's AWESOME,Why? Well i typically play on maps that are 45x45 at the smallest usually. This means i can get it into position early on, got a timberwolf? big whoop wanna fight? because the Karhu is gonna get there faster,Can't run over that hill? JUMP OVER IT THEN! this beast can not only run rings around someone for that extra sneaky backshot, it can for the most part jump where ever it wants. The Arcas in your star will drool and drink its milk in hope of some day doing what the Karhu G can do.
I haven't even gotten to the weapons! 1 improved Heavy large laser,3 ER Medium pulse lasers and Four count em FOUR Streak SRM 4's. Now your thinking "meh i would rather have 6s" Trust me they more than awesome when your behind an opponent...did i mention you get can behind people easily?
You can Alpha strike (i know who would wanna do that?) and as long as your Streaks don't fire your not gaining any heat, so alpha on!! However I suggest unless your getting one of those tasty back shots,stick to just the heavy laser and the mediums, with a couple Streaks just in case. You might end up running up some heat, but your jumpjets or supercharger can pretty much get you out of any jam.
Add to that? i know what more could it have!! Its got a light tag!, now your probably thinking "pfft" but if you have one of these near some hueys? You can see why the Wolfs decided they needed new borders as a wolf player has said to me after facing this mech.
Now its downsides. Its not a very long range mech, so your going to have to use your mobility to dictate the range of the battle and know when the gettings good. The Heavy laser does some tasty damage, but its a heat hog and has a to hit penalty which can tempt you not to wanna play with it. Against anything with reflect armor your going to be at a disadvantage..until you can use your streaks and kick the surly surat in the leg for double damage.
Over all i really love this mech as you can see, its not the best but it can wreck a lot of the rest.