I bought the original 500GB Momentus XT when it was first released, and have used it as my primary hard drive in several laptops.
I have heard that the newer XTs are significantly faster (they have double the flash, and more aggressively cache bootup files), so its probably improved a bit, I'd imagine. Not that the original was slow, its pretty awesome, and I'm glad I bought it.
It gets progressively faster over time - It needs some use to figure out what to put on the flash. At first, it will seem like any other drive. It'll take a couple cycles of your regular workload before you really start to notice the benefits. I've also noticed it helps stop Windows slowing down over time - Unlike any other PC I've used, I have never felt like I need to format and reinstall to get that "fresh Windows" feeling of responsiveness.
It mostly caches the small files that take a long time to access - Big files won't really get a speed boost (that said, sequential read speed is great). This means that the small amount of SSD goes a long way, since it doesn't waste space on sequential files that are going to be fast to read anyway.
It doesn't cache writes (although I heard Seagate are working on firmware to do that). This only really matters if you're writing lots of small files. This is the main scenario when the hybrid falls flat on its face.
My laptop sees a fair amount of use with Firefox and Visual Studio. Firefox is more responsive, especially with the suggestions when typing into the URL bar, and Visual Studio boots up very quickly. I also don't have to wait for it to finish loading startup programs (I have plenty of them, incidentally) - I can load up Visual Studio or whatever right after I've logged in.
Since my laptop has two 2.5" internal drive bays, I could've gone for an SSD + data drive combo, but I am glad I opted for the hybrid drive. I don't have to juggle data between a small SSD and a larger drive.
Also keep in mind that they are laptop drives - I don't know if the 2nd generation drives have fixed it, but the first gen had issues with spinning down too often when put into RAID arrays.
There was a big firmware fiasco with the first gen drives, people reported all sorts of nasty issues (especially with Mac and Linux OSes). These have apparently since been fixed. Personally, my drive still runs the original firmware, and I haven't noticed any issues. I haven't heard of issues with the second gen drives.
This is what you lose by opting for a hybrid over an SSD:
- Fast writing of lots of small files
- Instant speed (hybrids have to learn what to cache, takes a few usage cycles to reach max performance)
And this is what you gain over an SSD+HDD combination:
- Not having to worry about juggling data between a small SSD and a larger HDD
- Frees up a SATA port
- Can potentially speed up all your stuff, instead of just things on the SSD