"I have one of these 18–200mm lenses and, honestly, I love mine dearly. Now, you will see some photographers in forums online saying that these lenses are basically beneath them, because they’re not as sharp as they could be, or they’re not as rugged as the more expensive lenses, etc. Don’t let that throw you. I don’t know a single photographer that actually has one of these that doesn’t love it, mostly because when it’s on your camera, you’re never going to say, “Oh, I missed that shot because I didn’t have the right lens,” because it does it all in one lens. As for quality, I have a 30x40" print of a photo I took with that lens while on vacation, framed, and hanging in my home. Everybody loves it, and it looks perfectly sharp and crisp all the way through."
Scott Kelby, Digital Photography 3
I have used the ef-s 18-200 at a few trips, and just took a look at the exif statistics from them. I have many shots at the wider angles, a bit fewer at the medium lengths, and almost always a peak a 200mm. So, if up to 300mm would be possible without sacrificing much of today's performance, then I'm interested. I have made 12"x12" photo books made entirely of 18-200 pictures, and are very happy with them.
If I during travel are dealing with bags with clothes, shopping bags, kids, snack, tickets, and are jumping on and off ferries and buses, I sure appreciate not having to carry and change lenses.
I may more often use higher grade lenses, but wouldn't hesitate to recommend the ef-s 18-200 for general traveling and to beginners.