Glue fixes have their time and place. I will never travel for kiting without it. Last trip I had a LE puncture while self landing and was on the same kite The next day with no shop visit required. Tairaid on the bladder puncture, Dacron backing inside the LE and a 3x3cm grid/goop on the outside of the LE. Didn't even take out the LE cause it was close enough to a zipper access. I tried a double sided Dacron repair without glue and it would bulge too much and would have have torn there into massive repair on the first big crash. With the glue fix patch it doesn't bulge at all and you can tell just by looking at it at full inflation that is no more a stress point than it was before. Has held up solid for the season so far. Kite is worth less for sure, but its not new either. Glue fix/aqua seal is the bomb for valve repair too.
I agree with Starsky.... a Kitefix repair kit can be a huge life-saver on a trip during a good stretch of kiting weather/ or on a trip with no easy access/no time for repairs at a sail loft. I never go on a trip without a Kitefix repair kit + a good amount of dacron tape + a whole bunch of bladder patch + sewing kit + other board/kite repair materials.
I do not agree with the OP that using a "kitefix" system is universally bad. If done improperly, or used inappropriately....perhaps yes. But sending a kite out for loft repair is usually very time-consuming, costly, often involves shipping, and almost always lost time on the water. I some cases I would agree a loft repair is a nice option. I used to send kites to the loft without hesitations, but now I try to repair them myself with Dacron tape or Kitefix if those systems are appropriate.
I recently dumped a fairly new kite in big waves in Ireland and it tore the kite from leading edge to trailing edge...next day I had it repaired (with Kitefix) and was back on the water with it the next day after that. Total cost: about $15usd. Total time: maybe 2 hrs of work max.
Since then I have had this kite out in super gusty conditions, WAY over it's designed wind range, and the repair is holding fine. Same day a mate snapped his chicken loop because it was so gusty.. My confidence in the repair is 100%. I've done other similar repairs in the past and they are holding up fine as well.
If you look for the repair you will see it, but most people can't see it unless I ask them to look for it. And I am taking about more than a 5 foot long tear. Personally I don't care what the kite looks like - as long as it flys OK, and as long as I can use the kite again ASAP I am happy. I agree that it might effect resale value a bit...but personally, if done correctly and neatly, I don't think it devalues the kite any more than any other (sewn) repair. In some cases I've see a sewn repair job actually diminish the value of a kite if it was done poorly. A lot of times a loft repair job requires pulling many of the panels apart to do the repair and then reassembly. A repair job with the Kitefix system actually preserves the original construction of the kite more than any else. I'd say if it adds any weight it would be less than an ounce.
If the tear is such that it can be easily repaired with dacron sail tape that is my first choice. If the tear is bigger and more I like to use the Kitefix. Dacron is actually a great repair material because it has good dimensional stability due to the warp/weft of the fabric,,,,which allows it to flex and "give" according to the forces acting on a canopy full of wind. I have found that the ripstop tapes do not have the best adhesive qualities (inferior to th Dacron repair tapes)...so I might only use the ripstop tapes for very small pinholes and such.