This map diminishes the number of congressmen that the Democrats will elect. That's indisputable, but not surprising. What's also indisputable is that the map, as a whole, creates more minority opportunity districts, and that more minorities will represent Texas (and be Democrats, too) under this new map than under the old one which Democrats created.
Minorities do not get a bad deal under this map, unless you adopt the Democrats' apparent argument that all minorities have the constitutional right to be represented only by Democrats.
I don't personally believe that minorities get the shaft under this map; I'm just assessing how I think this challenge may fit into the jurisprudence both in Texas (Bush v Vera) as well as nationwide. In my personal view, the redistricting process should be blind to both race and party - basically determined by either nonpartisan commissions or bipartisan committees. That's not currently the case, however, and I don't know whether this Tyler court which issued the 2002 maps (where the challenge has been filed) is actually favorable to Democrats per se or just abided by the 'least-change' principle in issuing those maps. The general impression conveyed in media reports is that the court itself favors the Dem arguments, and if that's the case I simply think that there's more than enough room for interpretation to overturn the maps.
If it were up to me, I would reject the Voting Rights Act argument (in fact, I would strike down substantial parts of the Voting Rights Act itself as unconstitutional).