I personally like the challenge of the time limit. I am still new to photography, so my archived images are not that good anyway. I admit though that sometimes I rush the shot to get an entry, and this is probably pointless, as it does not improve my images. But I am always taking photos, so maybe there is one somewhere on my disk that will fit most themes.
Conclusion = after that ramble, you could sit me on the fence for this one.
