18-200 / 18-55 /18-135 - all kit lenses. Not necessarily known for speed. Not necessarily the sharpest lenses out there. But for someone that has no or little experience with DSLR's- I highly doubt that you would see the differences between almost any of them. There are people that absolutely love their 18-200's. There are people out there that love their 18-135's. There are people out there that love their 18-55's. And there are people out there that hate each and every one of them. They are kit lenses- basically a lens for the camera so that it is functional for those that don't know what they should get. It's an introductory lens. If you shoot Standard Picture Style, and shoot with your 18-200 at various focal lengths ( 18, 50, 100, 135, 200 ), at ranges that you would typically take a picture of- how does it fare? Do the pics look decent quality? If you stop down the lens some- from say 3.5 to 5.6 or from 5.6 to 8.0- how does the pics look ? 100% crops ?
Personally, I would suggest that you won't see that much difference between any of the standard kit lenses- until you purchase MUCH MORE EXPENSIVE lenses. And even then, the amount of improvement- well- to some- it's not that much- to others- day and night difference.
For my T1i, I kept my 18-55 because I knew someday, I would part with the T1i. And whomever bought it- would probably want a lens to go with it. I had better lenses- but I knew the day would come- so I kept it around.. I also loaned it out a few times- but I kept it so that I had something to sell with the body- I knew the day would come. I sold it with the T1i.
EOS 5D III, EOS 7D,EOS Rebel T4i, Canon 70-200 f/2.8 IS II, Canon 24-105L, Canon 18-135 IS STM, 1.4x TC III, 2.0x TC III, Σ 50mm f/1.4, Σ 17-50 OS, Σ 70-200 OS, Σ 50-500 OS, Σ 1.4x TC, Σ 2.0x TC, 580EXII(3), Canon SX-40, Canon S100
Fond memories: Rebel T1i, Canon 18-55 IS, Canon 55-250 IS, 18-135 IS (Given to a good home)...