I usually hang onto it for a week or two, look 
at it again (in case it's just your mood 
today)--and if it still doesn't do anything 
for me, I sell or trade it...the darned things 
cost too much (and accumulate too quickly!) to 
hang on to unless you really adore them.  May as 
well go ahead and free up the space and money so 
when the next (amazing) cel shows up, you have the 
resources to buy it ;)

of course, that may just be my current budget 
talking...paying off grad school (now that i'm 
finally finished!) and saving for the wedding is 
making me a lot more cost-concious of my cels!
rosemary