The new CS5 edition of Adobe Photoshop has refined the HDR (High Dynamic Range) processing. Now, you won't need the Photomatix plugin (in theory).
After selecting the 'Merge To HDR in Photoshop' option in Lightroom, the images get exported to Photoshop and it starts doing its magic. Normally (in the earlier versions) you would end up with a 32-bit image, but now you have the option of manipulating the 8 or 16-bit version of the image. Just like in Photomatix.
Photoshop CS5 HDR interfaceInitial experiences are not really positive, but that can be related to my experiences with Photomatix. A quick glance at the controls available, it should be able to produce similar results.
Talking of Photomatix; The plugin used in CS4 won't work in CS5. You need to download the CS5 version of the plugin at the HDRSoft.com website (Mac / Windows). The new version is universal (32 and 64-bit), free of charge to registered users, and works only in CS5.
One thing I didn't expect was that Photoshop started downloading a lens database from the Adobe website during the creation of the HDR. No idea if this is used in the HDR creation, or that this is done only once and used in other Photoshop CS5 plugins / filters