-> Two models I have been reading about are the "Nemesis II" by
-> Cochran Undersea Technology and the "Aladin Air X" by Uwatec. any
-> comments on these 2 computers?
Some very good divers have had some very serious problems with Cochran
computers.  Other, less extreme divers seem to like theirs very well.
Personally, I'd avoid them for no other reason than more than one person
has reported similar problems.
As far as I know UWATEC makes good computers, but the Air X, the
separate sending unit and hoseless readout on the wrist has been known
to have communication problems under some circumstances.  Check on this
before you purchase one.
Having done my best to answer your question, I'll offer some of my own
opinions on computers:
1. I don't like air integrated.  Most air integrated computers give
   you the lesser of now deco or air time at current depth.  I want
   no deco all the time.  I can judge air adequacy for myself.  Also,
   if you ascend from a few minutes at a deep depth to a shallower one,
   the air integrated computer will give you a false reading (shorter)
   until it adjusts to your new air use rate.  They measure pressure
   drop in the tank, not your actual breathing rate, and you use lots
   more air at depth.
2. I don't like wrist mounted computers.  I stick my hand in places
   I don't want my computer going, like after lobster.
3. A computer which goes way deeper than you ever expect and has
   full decompression or at least ceiling information is better than
   one that does not.
4. Don't even think of buying a computer which does not have a user
   replacable battery.  You won't like what the factory charges to
   replace one.
OK, so now you want to know what I use.  I have two US Diver's Monitor
I's.  This is not the new Monitor, it's the old one which is no longer
in production.  They are not air integrated or wrist mount and they have
ceiling decompression features.  They're good to around 350 feet, much
deeper than I'm likely to be and I've been diving for 30 some years.
The only thing they don't have is user replacable batteries.  That
feature was not available when I got the first one and I bought the
second one as a backup for when the first one has to go in for a $100
battery replacement.  When it's time, I'll have to think about what to
do since I bought the most recent one used for the same $100.
Lee
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