Currently I use the old favourite of trimix divers, the VR3 (or VR£, as it's sometimes referred to). It's a good computer on the whole but it's big and does not produce an ascent profile that I'm happy to follow without padding. It's also quite expensive.

However today I got to play with the OSTC MkII dive computer (see: http://deep-ideas.co.uk/Store/index.php?main_page=product_info&cPath=31&products_id=136). Unfortunately I was diving nitrox in Vobster so I cannot comment on the deco profile - however it's purportedly true Buhlemann with user definable gradient factors.

First impressions are that it's very intuitive to use - I was able to set it to 32% Nx without any instructions or prompting from the owner. Once under water it is incredibly clear and easy to read with a big screen on a small computer.

Comparison to others:

Size - much smaller than the VR3, Shearwater Persuit and D5. However it's bigger than the Liquivision X1. I think that it is a nice size (it's actually slightly slimmer than my Suunto Vytech).

Features - well equipped with all the features needed for serious 'mix diving. Not as well featured as the D5 or perhaps a fully spec'ed C4 VR3, but then nowhere near the price! A great feature is the Gradient Factor setting - you can choose more or less what you like rather than being limited to a pre-selected set like on the Sherewater. It has a constant PPO2 setting for CCR use, which the Suunto Helio2 does not.

Ease of use - the idea behind this computer is that the setup is done by plugging it into your PC or laptop and do most of the work there, however I did not get to try that so can't comment. All the settings (I think) can be set on the computer itself and it is really easy to use. Much easier than the VR3. Possibly users of Suunto computers could find their way around a Helio2 a bit quicker but not by much.

Price - at £620 it is expensive if you don't use 'mix, but it compares very well with the competition, certainly cheaper than the Liquivision and comparable VR3.

Final thoughts - I'm not going to buy it as a replacement for what I've got, despite the display being much nicer. But that's because what I have works and I don't have £600+ to spend. Neither would I go for it if I was moving across to deep CCR - I'd probably be looking at the D5 (or unlocking my VR3 to C4 spec as a cheaper intermediate step). However, if I was in the market for a new trimix computer, or a nitrox computer with a view to moving up to 'mix in the future I'd definitely look at this as one of my first choices.