I researched this same question extensively.
I ended up installing the Intel X-25 G2 160 GB (silver case). With the new firmware updates on this drive (dated Nov. 2009), it supposedly does firm-ware level cleanup and performance does not degrade with time.
By all accounts, the Intel SSD is still the performer of choice with a proven track record in the Macs.
Installed this drive, moved my 640GB main drive to the optical bay spot. My 640 GB drive was previously partioned with boot camp and Windows 7. It boots just fine into Windows from the optical bay.
I'm putting applications and the OS on the SSD, and leaving the hard drive for media and data. I've not seen a succient writeup on how to do this, so here's some general tips:
You should *keep* your /user account on the SSD. Certain library settings need to stay on this drive. You should move music, media, the itunes folder, photos, downloads, and e-mail to your data drive. This is a bit complex. itunes and iphoto allow you to specify the save directory (and itunes will copy your music). The download folder can be assigned in preferences. e-mail is the toughest. Here's the best instructions, from macperformanceguide.com
0. Quit Apple Mail, and make a backup of your mail folder.
1. Copy the Mail folder to the top level of your data drive (or elsewhere, then modify step 3 appropriately).
2. Rename the original mail folder to Mail.old as an additional backup.
3. Start a Terminal window and type:
ln -s /Volumes/Master/Mail Library/Mail
This makes a symbolic link to the folder Mail on the volume Master (type the name of your volume, and use quotes around it if the volume name contains a space character). The resulting file Library/Mail is a tiny file that says look over there on /Volumes/Master/Mail instead. Note: in this example, the data drive is named "Master" and the folder at the top level is named "Mail". If your's is different, adjust appropriately. This last step is essential to get mail to use an alternate drive as the storage directory. Not simple, but necessary.
Now, you've got apps and system on the SSD, data stored on the HD, and you get the best of both worlds!
I'm extremely pleased with the 160GB Intel X-25M G2. Best combination of reliability, performance, price, and size.
YMMV,
Joe M.