K-Pro experience
I've had the k-pro tour for about 2 months now and can add a few thoughts. i was previously using a Babolat Pure Storm Tour which is awesome on groundies but a bit heavy and not as maneuverable as I would like. The PST weighed in at 12.0 ounces with dampener and strung was only about 4-5 pts head light with a swingweight of 333. It got tiring playing hard into a long third set. I wanted a lower swingweight racquet that was a bit lighter as well. At first, strung at 60 lbs with a good multi, it felt somewhat stiff and too low powered, but I immediately noticed it was much easier to generate good swingspeed on groundies and serves. When I dropped the tension to 52, the frame softened up quite a bit, sweetspot got bigger, and spin production was much better. I know it sounds trivial, but I added just 0.5 grams of lead at 3 and 9 oclock and the pop/power improved significantly. The calculations suggest this should not have made that much difference, but it did.
BTW, all these specs need to be taken with a grain of salt and what you feel when playing is what really counts. The specs printed on the frame are for an unstrung frame ie 11.1 oz, 10 pts head light, without overgrip, etc. Strings typically weigh anywhere from 0.6 to 0.8 ounces and I believe string tension effects frame stiffness to a degree. Strung with a 16G Multi, dampener and overgrip, the weight was 11.6 oz; 7-8 pts head light and unknown swingweight. This is corroborated with what Wilson posts on its website regarding strung spec's.
Anyway, this stick plays amazingly well. Excellent power generation because its so easy to swing fast, but still heavy enough. No it will not crush a ball like a heavier frame when you have all day to set up and wail away, but when you're scrambling, off balance, and improvising, this racquet does a great job. And, it does not leave you tired after playing hard for 2-3 hrs (I'm a 4.5). Each player will find the best balance between swingweight, balance, overall mass, and string tension for they're own style of play and fitness/strength level. This one works for me.