Besides Nero, I was also able to create a valid Blu-ray disc ("valid" means it was playable by both PowerDVD and WinDVD 8 for VAIO, I did not test it on PS3) out of BDMV folder on a hard drive with following 2 methods:
1) On Vista, using built-in burning software: Insert the disc, right-click, select "Format...", choose "Live File System", select UDF 2.5 as file system (it will be default for Blu-ray). When formatting is complete (in 1-2 min), copy BDMV folder and possibly other folders (CERTIFICATES etc.) to the disc using Windows Explorer.
2) In XP, using Roxio Drag-to-Disc: Insert the dics, format it with Drag-to-Disc (it will use UDF 2.0 file system), copy folders using Windows Explorer, then go to "Options" in Drag-to-Disc, select "Eject Settings", choose "Close the Disc" tab, in "Advanced Eject Options" choose "UDF Version 2.5" for BD and clear "Add ISO/Joliet Support" checkbox. Click OK. When you eject the disk, the file system will be changed to UDF 2.5 and the disc will be closed. Disc created this way will be playable by both PowerDVD and WinDVD 8.
You should be able to use Nero InCD as well (unless it also adds ISO/Joliet structures to disc as it does with DVDs: PowerDVD does not like them).
With Nero, it seems you have to use Nero Burning ROM and manually select UDF 2.5 to create a valid disc. If you leave the default, or use Nero Express, UDF 1.02 will be used. (I did not use Nero Express on a real disc, but when I created a Blu-ray image with it, I ended up with UDF 1.02 - checked by IsoBuster).
ImgBurn does not create valid Blu-ray discs - it uses UDF 1.02 file system (which you cannot change).
Roxio EMC 9 "Home" burns with UDF 2.5, but also adds ISO/Joliet file system (and there is no setting to change this). Interestingly, WinDVD 8 plays such a disc, but PowerDVD doesn't (But PowerDVD will play a disc with UDF 1.02 file system if there is no ISO/Joliet, like that created by ImgBurn).
So Blu-ray is already very advanced IMHO: not only 25GB BD-REs are widely available and you can already buy BD-RE 50GB as well, but to burn them you do not need any additional software at all if you use Vista. You also do not have to worry how exactly files will be placed to the disc (as in the case of DVDs) - this is handled by UDF 2.5 file system. Also TDK says that you can rewrite their discs 10,000 times! This is just amazing.