OK, I tried it too!
I just put an Intel X25-M 40GB SSD into my Mini 2.1...
Here's my impressions:
SL/iWork/iLife install was nothing specially fast.
Updates also didn't seem any quicker, including the "writing files" part.
However, Boot time is way down. So is launch time.
The previous install was pretty clean with only the "SL Box Set" installed and updated. It was already pretty snappy on a 7200rpm 120GB Hitachi with 16mb Cache along with 4GB RAM.
System: Mac Mini 2.1 with 4GB RAM, 1.83 C2D, GMA950 graphics.
Boot Time: Halved.
Hard drive= 38sec
SSD= 20sec (from pressing power button to Finder)
Shutdown time: Halved.
Hard Drive= 3-4sec
SSD= 1.5sec
Sleep/wake times went from fast to practically instantaneous.
Heat levels as felt at the air vent on the backside are noticeably lower. Also, the fan runs slower. (Yes, I transferred the little foam piece on the bottomside of the hard drive to the SSD)
I never timed the original 1GB/5400rpm configuration but remember "Dashboard" being quite pokey and choppy when called up and especially when hidden.
The 4GB/7200rpm configuration caused Dashboard to operate much more smoothly.
The 4GB/SSD seems to have made an additional improvement, though it's difficult to quantify "Choppiness"
I can't say that an SSD had completely transformed the machine from the 4GB/7200rpm configuration... it was already snappy. It did make noticeable improvements in speed and heat output.
If it had been an upgrade from the original 1GB/5400rpm configuration it would have been a profound difference.
SSDs are going to be the way to go very soon.
But for right now plenty of RAM and a fast Hard Drive with plenty of Cache can give you much of the advantage with far more storage capacity.
This is especially noticeable with the Mini's slow 5400rpm/8mb Cache drive. That thing needed to go!
In the meantime this is one very quick Mini.
I can't wait until SSD's get big enough for my MP1.1
Have Fun,
Keri
PS. Quicker boot and load times are only part of it. There's much less Beachball-of-Doom. When it boots, the ball stops quickly and STAYS stopped.