I do like the look of sedum and sempervivums together but it definitely takes time to see what works with what. I normally use ground cover sedum types as opposed to the "border" sedums (the tall types) but even the ground cover types can overtake a semp bed over a couple of years. I have been looking for the smaller species/cultivars to companion with semps and only time can tell which works best for me as my growing space has gotten smaller.
Here are some pics from a raised semp bed with scatterings of Sedum (album, oaxacanum, sexangulare and 'Angelina')
After a year or two, the random scattering of sedums resulted in some of them turning into a bed of its own, or clustering into a big mound or sending out branches that covered the semps. Definitely a regular bit of pruning helps to keep it from covering its neighbors but I'm sure there are types that probably grow slower and more compact. It's a matter of finding those and incorporating them into any combo beds. The Sedum 'Faro Form seems a good candidate for compactness and color in smaller spaces. I like the color and look of the Sedum dashphyllum but one needs to also consider hardiness of the many types to see what would work in which zones
