Tried a Shearwater Predator (on rEvo) and a Liquivision X1 (OC)
Wound up getting the X1. I liked the display's viewing angle ability a lot more, and the fact that I can recharge the internal battery whenever I please.
It's completely sealed & potted with gel, so any servicing (I estimate replacing the rechargeable battery every 5-7 years) will require it to be sent back to the factory. I'm okay with that.. in exchange, I know it's extremely durable with nearly no chance of leaking.
Initial setup and software loading was mildly confusing (as I use OS X) but in the end quite workable.
The Predator, by comparison, has an O-ring sealed user-serviceable battery compartment. Not sure if the battery is available rechargeable or not, or of the cell type.
The particular model I used did not have a rechargeable cell.
EDIT: The newer Shearwater Petrel uses AA's, which is great!!
Another poster in this thread mentioned not liking the tap-style interface of the X1; conversely this is another feature that I enjoy. So far it's worked well with up to 7mm neoprene gloves while worn around a drysuit with no issue.
The settings for my X1's software include adjustable tap sensitivity.
The Predator uses a piezo-style pushbutton (no actual movement or dynamic seals) which is also quite nice. I had very little trouble learning to use the interface.
I guess what I'm trying to say is that you can't go wrong with either.
I purchased the X1 mainly due to personal preferences over a few minor specific features.
In the end, no matter what computer I use, for anything near/past NDLs I always back up with a depth gauge / timer and tables...