Personally, Assisted OTF knives are really basically useless, even in a knife fight (better then nothing, but there are so many better choices).
So the first question is what is the purpose for this knife? EDC, whittling, camping, nail trimmer, skinning, self-defense, pig sticker, etc.....
The problem I have with Assisted OTF is the blade locking system, most will let you down when you need them most. In a knife fight, hitting a rib with an OTF can be a big problem (blade releasing and retracting or breaking the blade lockup). It is also easier to break the blade off from the handle because it is the weakest mechanically.
Obviously for knife fighting a fixed blade is the best choice (my favorite is the Gerber Mark II) but not always the easiest to carry. The Mark II is great in the field/woods but not good at the mall so my EDC carry is the Gerber Covert Applegate/Fairbairn knife.
I have several Kershaw Knives, they are high quality and they stand behind their knives. They make an OTF called the Ripcord but it is not assisted so once open is more like a fixed blade.
There are tons of good knives out there, KA-Bar, Gerber, Boker, Kershaw, Microtech, Benchmade, CRKT, SOG to name a few.