Maybe do the migration only on the applications, other and settings; use restore afterwards to restore your user info. What I can't recall is that when you use restore if you can redirect it to another volume. And since this is a new system, Time Machine may balk at "restore" since it views it as a whole new computer.
Let us know the answer
this could be a common problem.
Rob
Thank you all for your feedback; I've used the advice posted above in part, preceded by the need to move the Home folder to the HD. It's indeed a fairly common question which hasn't been answered in a very clear way so far.
And why is this? Because OS X's Migration Assistant is still based on a premise of single-drive setups - therefore, ONLY startup volumes can be used for the migration, unfortunately. However, I am sure Apple will have to revise this stance soon, with the increasing adoption of SSDs alongside higher capacity HDs.
So let me list the necessary steps for accomplishing this interesting experience:
1) My 1TB HD was recalled by Apple, so I took it to an AASP and requested also the after-market installation of an internal SSD (the 120GB OCZ Vertex 3, considered as one of the fastest and most reliable in the market, with SATA 3 support and SandForce controller - no native TRIM, though, which is not even necessary anyway for SandForce-controlled drives).
2) After confirming that I had bought Lion already, the AASP clean-installed it again on the SSD;
3) Since I have a boatload of content in my home folder, I had to install this folder in the HD;
4) Once Migration Assistant popped up (AFTER THE CLEAN INSTALL), I didn't do anything and just created a NEW user with EXACTLY the same short name and password as the previous one I had;
5) With this new user created, I then used MA to transfer all my apps and System-level settings and files into the SSD;
6) I then copied my NEWLY-CREATED user folder back into the HD (such a folder was, of course, almost empty at this stage) - this step is necessary so that you can remap the home folder as per step 7 below; following that, I went to System Preferences/Users & Groups, and right-clicked on my user to open up "Advanced Options";
7) In there, I simply selected the NEW place where the newly-duplicated user folder was in the HD; do NOT change any other setting unless you know what you're doing;
8) I then carefully selected, FROM my TM backup, the most recent backup folder and navigated to my old user folder in order to copy everything from there to the aforementioned "new" home folder in the HD (docs, media content, library settings, mail, application support folders, preferences etc.);
9) Once you reboot, you will see that your HOME FOLDER is the one in the HD, and not anymore the previously-created SSD-based home folder (which can be deleted after you confirm all is OK with the migration);
10) So far I've only had a few permissions issues (which can be easily solved by going to "Get Info" and checking whether your user can read/write to such folders/files).
I did the same with my wife's home folder, so BOTH user folders are in the HD, with plenty of space available.
Bottomline:
120GB SSD - OS X, all main apps and System-related files (including swap files as necessary) - after doing a lot of reading on this, I'd recommend leaving some 20% of free space on the SSD for performance reasons;
1TB HD - ALL user folders, media (iTunes, iPhoto etc.), user preferences, user-based application support files and documents.
Feel free to take the steps above at your own risk (there shouldn't be any major issues if you carefully follow the sequence, I think)...I just hope this helps every other person trying to do the same thing..!
p.s.: And yes, despite a few minor bugs, Lion ROCKS and continues to be absolutely solid for me.
So far, no kernel panics, no media crashes, no slowdowns. Version 10.7.1 will only clean up what is already a VERY stable release.