I am a new diver, so my experience is similar to the OPs. I purchased the Oceanic Nav console with the VEO 180. I have used it on four dives now. Here are my observations:
1. I like that I can download the dive profile and analyze my dives. As a new diver I still need work on rates of depth change. I tend to go too fast. I have not been able to effectively use the rate display while I am executing a depth change (too many other things to watch). So this function has limited utility for me. Maybe when I get more experienced. I can see where it would be good if you were following an anchor line up or down; I have only done quarry dives since the purchase.
2. I actually like the cycling planning display. For example, if I know I am going to restrict the next dive to say less than 50 feet. I know it is safe to dive if the planner shows an available bottom time longer than my air supply.
Last week I did a couple of shallow dives with my youngest son. We did not exceed 40 feet on the first dive which lasted a little less than an hour. Knowing the second dive would mirror the first, I could see how much bottom time we could safely get at planned depth. In this case, very little surface interval was required. By the time we had a sandwich and drink and prepared our gear we were good for a 3+ hour dive at planned depth.
I am new and cautious so I made sure we were very liberal with the SIs and that I compared what the computer was showing to the tables. I would be more confident if I was diving with someone with a computer and compared data. For this reason, I am going to invest in a computer for my son.
3. I am not sure about the alarm being useful. I have had depth change rates that should have activated the alarm, but I have not heard anything. I am wearing a hood so that may be a factor. Next time I dive, I will try to set up a circumstance deliberately to set off an alarm and see if I can hear it. Of course, the problem may be me as I am 63 years old and was an Air Force pilot for 20 years, then a commercial pilot for another 17 years and the jet noise may have killed my hearing in that range.
I am very glad that I invested in the computer. It is helping me be more aware of my dive profiles and helped me be more comfortable with planning and surface intervals. My son and I only have seven dives where we were solely responsible for the planning.