In general, they are poorly thought-out pieces of old technology that are neither user-friendly nor well-supported. The number of threads on SB where someone can't get basic parts/service for their 1, 2, or 3 yearold Suunto/Oceanic/Mares/Scubapro/etc. are leigon.
Beyond that, they're not very good dive computers: read the manual for an Atomic
Cobalt or a
Shearwater sometime (stick to the OC only mode for Shearwater, because while it's well-designed, there's nothing simple about the Closed Circuit mode). I think you'd agree these manuals are short, easy to read, and intuitive -- because they're explaning the workings of a dive computer with a well-designed user interface.
Then go read the manuals for some of the "full-featured" recreational computers like the Suunto V
yper or the Scubapro Galileo
Luna. They have a lot of overly-complicated features (see, e.g., the alarms on a Vyper, or the picture maps on a Luna), navigating their menus and setting options requires having the manual in front of you
and flipping around in it constantly, and their attempts to idiot-proof their products lead to weird limits like deco violation lockouts and the following stupidity from the Suunto Vyper's manual:
The Error mode results from omitted decompression, for example, when you stay above the ceiling for more than three minutes. During this three-minute period the Er warning is shown and the audible alarm beeps. After this, the dive computer enters a permanent Error mode. The instrument will continue to function normally if you descend below the ceiling within this three-minute period. When the dive computer is in the permanent Error mode, only the Er warning is shown in the center window. The dive computer does not show times for ascent or stops. However, all the other displays function as before to provide information for ascent. You must immediately ascend to a depth of 3 to 6 m/10 to 20 ft and remain at this depth until air supply limitations require you to surface.
I don't know who thought that depriving a diver of best-estimate deco schedule information (likely already in an emergency situation beyond their training if they're using this computer on a deco dive) because they were 1' above a ceiling for 3 minutes was a good idea, but they should be taken out back and shot. As an aside, in large part I think the complexity and lousy UI is driven by the weird 1990s screen tech most of these use. You can only cram so much stuff into a UI based on those screens, and it show when you look at the graphics in the manuals. Again, compare that to the graphical UI for a Cobalt, Petrel, or Predator.
In sum, the appeal to recreational divers of these computers seems to be in their mass-marketing, lack of scary 'technical features' (which are probably simpler to understand than most of the features in the recreational computers (see, e.g., gradient factors), and supposedly helpful recreational features that are actually implemented in a messy, difficult to use way. In contrast, getting something like a Petrel won't cost much more (a used Predator will probably be less and still get good support from Shearwater) and will offer them a simpler, more flexible, easier to use and understand computer. This applies to obvious use while diving situations (e.g., jump in with nitrox 36 but realize at 10' your computer is still set for air), but also to things like dive logging. Read through the manual for the average Suunto or Scubapro computer and tell me how hard downloading a dive or uploading a firmware upgrade looks--do it on a Shearwater and it takes a minute or two using built-in Bluetooth.
These things aren't all junk: some are cheap enough that they fill an important niche, like the Zoop. But things like the D6i cost almost as much as a Petrel and deliver almost as little as a Vyper. The Luna is one of the worse offenders in the 'high price for a terrible, complicated, old tech computer' category, IMO. It's the Ti-89 graphing calculator of dive computers, except that it has an IR interface (1990's Apple called, they want their soon-to-be abandoned tech back).
This debate is not unlike the push of backplate & wing rigs into the mainstream BCD market. It's not just that these are better pieces of gear for technical diving...they're generally better pieces of gear for diving, period. Do you have to have one? Hell no, nor do you need a fancy BCD or recreational mainstream computer. And if there was a big price difference, you wouldn't see this kind of recommendation as much. But all too often you see newer divers thinking of dropping $500, $600, $700 on a shiny new options out the wazoo BCD rig or $600, $700, $900 on some crappy Suunto or Scubapro wrist computer...when for that much or a couple hundred less, they could have a better designed, better built piece of gear that does more for them as divers.
