So I was running out of space on my MacBook Pro (non-unibody) HD, so as I am want to do, I upgraded the internal drive using Time Machine.
My history was that I started with a 250GB, moved to a 500GB, moved to a 640 GB, then to a 500GB Momentus XT, then to a 750 GB WD (7200rpm), now to a 1TB Seagate SSHD Hybrid (onlu 5400 rpm). Just some impressions - it's both slower and faster. It seems to lag on disk access when it's not cached, but snappy in general use, as I suppose is expected for the hybrid.
I would wait for the WD hybrids that come with more NAND flash, but I need the space now - it occurs to me that Mountain Lion is really a free space hog, and needs the space to operate smoothly. Before I upgraded, I was operating on about 50GB free, and heavy apps would completely bog down my machine. But even on first boot with more space free, I was operating smoothly again.
Hopefully this 1TB hybrid works out well and gives me another year or two out of old trusty.