I've been using a Lee 20 lb. for the past 7 years. These days, about 95% of my casting is for blackpowder rifle competition.
I've cast about 7000 bullets out of it, in lots of 50-60 bullets at a time, which equates to about 125 separate casting sessions. It does leak a bit from the bottom spout (I cast with a dipper), but other than that, it's been working fine.
However - if it ever breaks down, I'll replace it with the RCBS. At the time I bought it, though, the price difference ($50 vs $200, as I recall) was very important to me.