I have a pre97 ARB snorkel on my 2000. The snorkel itself is the same but the newer style includes the washer bottle relocater kit which adds about $100 to the price. I recommend using the old style and find a different washer bottle to use saving you the $100. I pulled one from an older XJ in the junkyard. Its the washer bottle that mounts in the engine compartment between the air box and brake booster. My 2000 brake booster is larger than the older jeeps, so I had to dent in the corner of the bottle to get it to fit. The holes for the washer motors also needed to be enlarged slightly, but it was a very easy bottle to use.
The snorkel is a true cold air intake, but don't expect to see huge gains in fuel efficiency from it.
Rain is not really a problem either. The first day I had mine it was raining all day. I drove about 30 miles freeway and 10 miles around town. The next morning I opened the air box to see how much water it took in and there was only a small amount in the bottom. So rain isn't a concern unless it is a HUGE downpour and you will be driving a long time in it.
Also someone metioned the exhaust. Don't worry about it. I can say that from personal experience from getting stuck in 4 ft of water. Exhaust was fine.