So far in any reviews I've seen real-world tests in, this drive performed better than desktop HDDs. For example, for application launches, the performance takes effect from the second launch after installation, but unlike memory cache, the performance is not lost after a shutdown or reboot. This page on AnandTech gives a couple of timing examples, some results which are closer to SSD performance than even the WD Velociraptor, with a traditional 2.5" HDD far behind.
For a desktop PC, it's hard to beat a combination of an SSD for the OS/applications and a big hard disk for everything else, based on my PC's performance. But for a laptop, this appears to be an excellent choice, since up until now, you could either have a HDD or an SSD, but not both in most laptops.
4GB may not seem like much, but remember that it only caches small blocks of data read more than once and not larger blocks of data where the lower NAND latency has little benefit. For example, if Windows reads a lot of small files (e.g. 1000 DLL files during a application launch), most of the time is spent waiting on the HDD seeking for each file, however, if Windows reads a single file of the equivalent total size, the HDD only has to seek once (assuming no fragmentation) and the rest of the time is throughput related.
This hybrid appears to do badly in synthetic benchmarks, however, who cares if a drive performs miserably in synthetic testing and simulations, as long as it does well in the real-world practical use. To give an example, I have the first generation Kingston 128GB V series which I bought at a clearance sale (almost half price), a drive which did miserably in some reviews I read, a few even claiming it did not even stand up to a 5400RPM HDD in their tests. Yet, after mirroring the original HDD in my laptop to it, there was a drastic improvement, e.g. the boot time going from 90 to 30 seconds and applications launching about as quick as my desktop PC which as an OCZ Agility. I bought it to speed up the laptop, not to benchmark. :disagree:
I do agree with vroom, as a desktop hybrid HDD would be very nice and probably cheaper to make. :iagree:
Here in Ireland, the Momentus XT 250GB is priced at â‚¬99. The cheapest Velociraptor is â‚¬147.57 for the 150GB model and the cheapest SSD is â‚¬87.50 for the Kingston V-series 30GB I came across. So for a little more than the price of this 30GB SSD and performance appearing to be somewhere between an SSD and a Velociraptor in practical use, it appears to be a great bang for the performance.