In general, I don't see a lot of use of an SSHD on the desktop, at least not with only 8GB of NAND. There are significant advantages for a system (such as a notebook) where there is only a single available storage option.
However, if you have the capability to have both an SSD and an HDD you have a couple of much better options (e.g. on a notebook with an mSATA port or any desktop).
1. Install OS to SSD, manually manage installing things to HDD.
This will generally give you the fastest performance for the things that really need them, but you're losing a lot of your SSD to OS + hibernation file (if enabled) and you have to know how to manage multiple drives effectively.
2. Install OS to HDD, dedicate a portion of the SSD to caching (e.g. with Intel Smart Response Technology) and use the rest for things you always want SSD performance with.
This gives very simple drive management - by default you install everything to the HDD. The SSD caches the most-used stuff and you can manually move things which benefit most from SSD characteristics to the SSD. Definitely the easiest setup to usefully use an SSD when setting up a machine for someone else.
BTW this is how I've got my ultrabook set up (32GB SSD cache, 80GB SSD data partition). The 32GB of cache is approximately equal to the Windows 7 OS + Hibernate file (16GB RAM) so I'm not really losing any space, but it's being used more usefully. And things which greatly benefit from fast random access (e.g. source code trees) are on my SSD.