I agree with the general consensus here, but I want to make you aware of WHY the serrated blade works well.
First of all, a straight blade that is properly sharpened and honed will cut rope as well (or better) than a serrated blade. The reason a serrated blade works so well, is because you have a longer cutting area because of the 'waved' pattern and also because the fine edge of the serrated area only contacts a solid cutting board for example, at the very tips of the cutting edges- the 'raised' areas. So, the perception is that the blade cuts better and / or stays sharper longer, but how well it cuts has much more to do with the quality of the edge (how well it is sharpened and honed), and holding that edge depends on the alloy used for the blade.
I use and suggest D2 tool steel. The edge holding is fantastic, but it will rust if not cared for properly. I use a Benchmade pocket knife, but many companies use this alloy now.
So, I undertstand all this and still carry a 1/2 serrated blade. Why? Because usually when you need it most, you are miles away from the nearest honing stone, and the 'preserved' edge of the serrated section is good to go.
Oh, and for cutting seatbelts, get a specialized tool for that. There is nothing worse than laying someone (or yourself0 open trying to cut a seatbely with a pointed blade. The safety cutters (Benchmade has these as well- like $25.00) are far better, safer and effective at the task of seatbelt cutting. If you are an EMT, at least have your pocket knife blunted on the tip...
If I could have only one knife for ever, I would have a straight edged, fixed blade knife (and a sharpening kit). That will last me forever...