I've only ever run Deore front derailleurs for singletrack/XC riding and I've never had a problem with them. Keep them clean and adjusted and they have always worked great. Now I have to use a Deore FD on the bike I am building (because of the chain ring sizes) and I was wondering if I should use the Deore FD I currently have on the Rockhopper and upgrade the Rockhopper. I can get another new Deore cheap but will I see any performance difference by going better? Any thoughts on the SRAM X Gen versus the Shimano stuff? If I did go up, I'd look at the XT or the SRAM.
So basically, the pros for the Deore are: cheap, as light as the XTR FD, and have worked great for me. I don't have any cons because like I said, I haven't used any others.