I haven't donated clothes in a while (since I now work from home I don't go through clothes the way I used to) but when I did I'd keep track and it was usually worth a $100 to $200 deduction every year, I'd say it was worth it. I used Turbo Tax's "It's Deductable" and as long as I had a list of what I donated handy when I sat down at the computer it was pretty painless. When I put the clothes into the garbage bags before I'd head down to the shelter, I'd just mark down each item as it went into the bag (shirt, pants, skirt, etc. plus the condition it was in) and then I'd take that list along with my receipt from the shelter and put it in my tax file so it would be handy at tax time.
Really wasn't much work at all, just added a couple of minutes to baging up the clothes.