Having read through their forums, I have some more information!
It appears that there are two options to playing the game - they seem to offer an install through a downloaded installer as well as though the beamdog client. One can download as many times as wanted through both routes when the game is purchased. Both methods are DRM free (except for the inital download) and do not require any internet connection after the game is downloaded to function. The only difference I can discern between using their client and not using it is that using the client will automatically check for updates if you have an internet connection - a pretty minor difference.
Also, if you get it on a mobile platform, the extra content (new characters and areas) are not automatically included, and the game costs less. The extra content will be distributed via app, and the cost for everything will be the same as the cost for the PC version (which includes everything).
There are plans for continued releases of support and DLC. The DLC will mix free and paid, though they claim that free will be the majority. They are also taking requests for DLC to be created in the future (within limitations). They are also allowing suggestiong of what parts should be changed from hardcoded to softcoded (within limitations). It's really great to see the modding community, which has been working away for almost a decade and a half, determining the ins and outs of the system, finally have an opporutnity to change all the limitations that they were working under and be able to do so much more.
Multi-language support is enhanced, with seperate options for text and voice-acting in different languages.
The graphic systems have been completely revamped. The rendering processes have been reworked, and the interface now supports a huge range of resolutions in high-definition, with support for zooming in and out. The interface is customiseble and moddable. It has also been confirmed that some content from the One Pixed Productions mods will be included.
In addition to the old music, voicesets and portraits, there will be new of each. The music will be scored by Sam Hulick, who also produced the music for the Mass Effect series. Portraits will be produced by Jason Manley, who used to be a portrait artist at Black Isle (I know he did some promotional artwork for SoA, I don't know what else he did).
That's the good news, and it's pretty good news at that. The worries about beamdog clients and DRM have been averted, there's new content going to be released (though depending on how much the paid stuff offers, there could be problems there) and the talent they have working on it has some very nice portfolios. Unfortunately, there's also some bad new to accompany it.
The original art assets are all lost, and replacing them is beyond the scale of the enhancement. That means that the areas cannot be rendered in any higher definition than they are now. It also means that there will be no new sprite animations and visible weapon/armour styles. New monster types are also not going to be added.
The only material that the devs have access to legally is from the BG series. That means nothing from Icewind Dale or Plancescape: Torment. Every part of material is off-limits, including portraits, monsters, spells, and sounds, unless that material is also in the Baldurs Gate series. It's still possible (and indeed I reckon likely) that the fanbase can port material form the other games (perhaps even with a creation similar to BGtutu), and the devs have no problems with that, but it will have to be undertaken by the modders without any official support.
Concerning altering of the old content (maps, encounters, NPCs), they have both legal and resource problems. They can add new encounters, tweak existing encounters, tweak items and item locations, and add minor text-only dialogue to characters, but that's pretty much it. They don't have the resources to redo everything, and their contractual limitations mean that everything they add has to be an expansion of the game and not significantly alter the original content.
All in all, though, the pluses far outweigh the cons, and some of the even negate them. For example, one of the things which is high up on the to-be-softcoded list is the animation files, so even though they won't be able to redo the animations they'll be able to open them up to the modders.