I bought the Oceanic about 3 years ago and used ot for about 5 months. During that time, it served me great. The PC software was lacking at best. After 5 months, I was on a dive breathing nitrox at 28%. I set the computer to 28% and started the dive. After the dive was over, the computer told me the mix was set to 71% (The computer as designed would not allow mixes greater than 50%)
Oddly enough, the exact same thing happend to my buddy on the next dive. His spiked to 55%.
We went back to our LDS and the owner took them back no questions asked and gave us each new Suunto Cobras. I will agree with everyone that these are more conservative computers. Over time, I have discovered that you can increase your bottom time on them by slowing your ascent rates considerably. 10 - 15 fpm not only keeps the computer from penalizing you on subsequent dives ( as faster than 30 fpm will penalize you bottom time on later dives ), but I truly feel less tired after diving as well.
You can also get more bottom time by ascending a few feet every now and then. Say I started a 90' dive, when I start approaching the NDL, I ascend 5 - 10' and get 10 or more minutes added to the NDL. The RGBM algorithms used in the Suunto designed by Bruce Weinke allow for instant recalculation of the NDL on the fly as you ascend. Also, should you go into deco on a dive, the computer will not enforce a stop if you work of the obligation in shallower depths. A slow rolling ascent is key for extending your bottom times as well as eliminating deco obligations should you accrue them.
Additionally, the software on the PC for the Suunto is outstanding compared to the Oceanic. I recently switched from my Cobra to a Stinger and I absolutely love it. A full funtional dive computer on my wrist, and it is barely bigger than a watch.
Hope that helps.
--Rick