I've got 2 framed cels. 
The first is my very first cel. I bought it way 
before I actually started collecting cels. I got 
it framed professionally and it came out a treat. 
In fact the framing ended up costing more than 
the cel itself. It was well worth it though.

My other framed cel was bought already framed.

It just feels great to have them brightening up 
the place. 
The only thing is they are probably more 
subsceptible to fading (even using all the 
correct materials) than if you kept them in your 
cel books etc.

Also, make sure you get someone who has had 
experience with cels if you are going to get it 
done professionally.

Anyway, hope this helps,
-X