This problem is generic with R-Drive, meaning you are not the only one suffering from it. My guess is that it relates to how R-Drive interprets dynamic disks if they are software raided. I have currently been evaluating R-Drive on some of my clients 2008 Servers some have hardware raid and some use Dynamic disks for software raid. However, i did not experience the extreme amount of time you are referring to, but these are pretty powerful machines (dual quadcores HP ML350 with 20GB ram). But yes, it takes considerably longer time to perform then on non Dynamic disks.
On one of the testservers we have a Exchange database on a separate RAID-1 setup (using soft raid-1, dynamic disks). R-Drive sees both disks in the RAID but you cant image one or 2 of them, you can only select the Logical volume in the RAID (this however makes sense, R-Drive probably dont know if its a RAID-0,1,or 5 software raid and imaging single disks in anything but a RAID-1 would seem rather idiotic). The raid array is 250GB, eg it consists of 2 250GB dynamic disks. If you select the option to do a full sector to sector image it appears as R-Drive will actually image both drives even they are identical. Why? Well, the backup archive becomes very big. The ecxhange database is only 17gb big. The resulting archive becomes around 70GB with max compression. Ofcourse, its no wonder it gets bigger since its a full forensic capable sector-2-sector copy. However, a full sector copy of the same raid drive using Paragon Disk Image Server results in an archive that is only 20GB. The difference is, in Paragon you can select any of the dynamic disks individually or both. If i select both, the archive grows 100% which seems logical but the restored (and archived data) is actually the same in both cases. Running R-Drive imaging on the same setup choosing only to backup sectors that has any relevant Data in it results in an archive around 14-15gb with max compression. Im not saying Paragon is a better choice here, R-Drive has several other benefits over Paragon which has made me to choose R-Drive in favour for the production stage i just mention it as a reference. A whole day for a 160GB drive sounds like alot though, but it could be the lack of VSS im not sure, i have had some extremely long backuptimes with Acronis before on rather small , but live systems. All in all, R-Drive is rather fast, and certainly amongst the fastest when using maximum compression in my experience. A hardware raid-10 of 300GB takes R-Drive around 2 hours to finnish on a Dual Quad Xeon w 20GB ram. Image is sent over Gigabit network. It takes the closest competitor almost 4 hours to finnish the same task that i have tested.
However, yes, there is something to look into when it comes to Dynamic disks. Or , i would say probably not the dynamic disks actually but i suspect the "problem" lies in how R-Drive images software-raids or how it interprets the array. For a Raid-5 you have a minimum of 3 disks also, i dont use Raid-5 at all at any of our clients setups as i have found Raid10 far more superior in that it doesnt take any cpu calculation and it has almost no performance hit at all in the case of a disk faulting. Moreover, you dont have to sacrifice performance either since u get both the benefits from the raid-0 and simple mirroring. Rebuilding takes no calculation hits on the cpu either since its just a disk to disk mirror. Ofcourse this is my personal experience and opinion and im sure many would beg to differ. We all have our "personal" pros and cons. But the fact that your software raid is Raid-5 could also relate to the extreme amount of time it takes. The complexity behind a Raid-5 is far more complicated then a RAID-1 or RAID-10 and i have many times experienced that imaging RAID-5 takes considerably longer time, however im still not suggesting a whole day would be normal, but it could depend on the HW. What about the sizes of your final archives, and ofcourse, do you backup only the useful data or do you perform a full sector by sector image?
As for Virtual server. I have imaged disks containing live running systems for Hyper-V. Which also use VHD disks. They will work fine when restored, only that u will get the message from the VM guest why the computer was shutdown unexpectedly when you first boot it again. This is perfectly normal. So im pretty sure there should be no problem imaging MS Virtual server either. You can also image directly from within the guest VM. But that also means you need to purchase 1 license per VM. Considering the price of R-Drive is very affordable this could also be a recommended option.
Hope this sheds some help