Almost exactly the same question was just asked here in this post. At any rate, the answers might be similar, so you may want to look at that thread.
There have been two or three versions of the EF-S 18-135... The latest is "STM" with improved AF speed and performance. It's a nice range of focal lengths, pretty capable of nice images and a comfortable single lens/walk-around lens solution. But it duplicates focal lengths you already have in your 55-250. It's definitely a step up from the cheaper 18-55 kit lens. But it is "crop only" (EF-S), which might be fine since most folks will stick with crop cameras, not to mention that many who think they "need" full frame, really don't.
The 28-135 is an older lens, but still quite good and capable. It's a particularly good value on the used market at about $200 typically (sells new for close to $450). There are tons of them around, many have been sold as kit lenses on 40D and 50D. But it's not a typical kit lens in build or performance. I've used several over the years and have one now. It's a convenient walk-around lens, has fast/accurate USM AF, is usable on both crop and full frame cameras, is quite close focusing, has reasonably good and useful IS (similar to the 18-135), and is Canon "mid-grade/gold stripe/USM" build quality. Negatives, it's not wide at all on a crop camera, it tends to have "zoom creep" (there are DIY fixes for that), and it's a wee bit soft at the longest 135mm setting when used at it's larger apertures. Otherwise, it's image quality is pretty competitive with the far more expensive 24-105L. Of course, it also duplicates focal lengths you already have.
Would the 28-135 be useful to you? Only you can say. I use a 12-24/4 Tokina wide angle lenses to complement it on my crop sensor cameras... so it works out well for me because I already have wider angle covered. You don't, so if you like/want wide angle, this might not be a good choice for you.
The prices on those used lenses at least seem in line, assuming they are in good shape and work well.