It looks just as good, if not better than crape's. I may even replace one of my crape myrtles for it, the purple is so elegant, its hard just to find a purple crape myrtle.

We use a mix of crape myrtles and Vitex in our barn area (we live on a ranch) as we are summer dry here, and things are dusty and drab and the brilliant colors of the flowers are great at that time of year.

While the flowers are beautiful, both shrubs spend a goodly part of the year not just flowerless but also leafless. They are amongst the slowest to leaf out in spring. The crape myrtles, especially if one is careful about the variety, at least have great bark and some have wonderful fall color. The Vitex have neither. The Vitex (speaking specifically of agnes castus) also have unfortunate branching habits and occasionally aggressive suckering. Each gardener needs to decide if the tradeoff is worth it, and if the chosen spot will benefit from the flowers more than the off-season shrub will detract. They may die back in your zone, in which case you may get a different growth pattern. The blue color on the Vitex IS stunning, and as noted above, is difficult to duplicate in a shrub.

They would be hardy in places one wouldn't expect, however the planting zone impacts the length of their performance. We have one in zone six and it's been a reliable performer in summertime. Like the previous poster says above it does spend a good part of the year not only flowerless, but leafless, at least here and has a lot of woody die-back in winter and needs to regenerate growth each spring. When it does bloom, it's really lovely. In our area, I would not ever put this shrub in a bed where I needed to depend on it for 4 season interest.

They are being used more down here than previously. The foliage has a nice green color to it. The flowers tend to last about 3 weeks on average. They grow wild down here in some of the moister areas.
For Zone 8, other good Crepe Myrtle replacements are Texas Persimmon (white/greenish flowers) and Texas Mountain Laurel (purple flowers).

Wow, pretty. I just bought one about 2 weeks ago and planted it. It's about 3 feet tall, well-branched, and has a number of flower buds, so almost instant gratification. I expect it to perform here as a dieback perennial similar to the way C.M. and butterfly bushes do.

Vitex is supposed to be not hardy here in NJ either, and mine has never died back, so you may be pleasantly surprised.