Things I liked:I purchased the .25 caliber version of the GTK290. This is one scary accurate and super powerful gun. Using a EOTech 512 1x scope, I was able to shoot 1/4" groupings at 20 yards fairly consistently. At 10 yards, I was able to place pellets through the same hole without much effort.
The look and feel of the gun is awesome. Everyone I have shown it to really is impressed as well. The adjustable cheek height is meh. Getting used to the electric trigger is easy and firing off the entire clip in a couple of seconds is easy. The battery can be upgraded to a Lipo easily though the OEM battery is quite sufficient. I typically get 35-40 shots between refills (I refill at 125 Bar). The long picatinny rail provides limitless options for mounting optics and accessories. There is little recoil and the weight and balance is quite good. Smaller or petite shooters should be just fine with this gun. Things I would have changed:Include a user manual. Reduce the noise of the report. Add the capability to change the length of the adjustable butt stock.
What others should know:The gun is not really backyard friendly due to the loud report when being shot. If you have over 200 feet between your house and the neighbor, you might be fine. I highly recommend purchasing a Premium 12 shot magazine, it's an accessory well worth the added cost. I found the JSB Match Diablo King 25.39 gain pellets to be very accurate and trouble free.
Be careful when loading the magazine. If the magazine is not seated in place perfectly, you will jam and lockup the gun and the fix requires taking apart the gun and ensuring you mark the location of the bolt at the point of lock up. When re-assembling, the location of the bolt must be exactly where it was prior to disassembly or you are in for trouble.