I have been skiing competitively for the last 20-25 years. I took up road and cyclocross racing about 4 years ago and am now hooked. Have made it to Cat 3 and now I have decreased the amount of time spent training for waterskiing and increased my cycling training. Lost 20 pounds, which actually improved my water skiing even though I am training less for it.
I have to agree with Shane that it is much more rewarding competing in ability based divisions vs. age based divisions. Plus the amount of time spent at bicycle races vs. water ski tournaments is a consideration. For example, I can complete a 50 mile race in a little over 2 hours whereas I would sometimes spend 10-12 hours sitting around to get 3 slalom rounds in.
I haven't completely retired from water skiing, yet. But it is definitely now my 2nd favorite summer activity. Something needs to change in the sport to renew my enthusiasm.