I've been working as an Oracle DBA in one of the global top 5 IT services companies (and with that said, I only mean that we have a lot of other companies that we host and manage, and im not implying that im a hot shot DBA) for 12 years. Hosting 150 production databases with many diverse setups is a joy to experience. I've worked in both dev and production teams. I've never worked with any other DB, but im a Linux fanboi and would love to get to grips with postgresql as it fits more in line with my ethics than Oracle does.
Long disclaimer aside; I crave comparisons such as this, but every single time I realise that they are all just anecdotes, and every dba on the planet has their own anecdote. It's hard to find comparisons on the Internet from people that are actually qualified to give such comparisons. The closest we can get is face-offs with the likes of Tom Kyte or Jonathan Lewis against similarly experienced MySQL/Postgresql experts. Many Oracle DBA's are also very arrogant, in my opinion, so these anecdotes tend to fly fast.
my experience is that Oracle is extremely expensive, but i've never dealt with paying that money so i've no appreciation of just how bad it can get. Oracle has some technologies like RAC, Data Guard, partitioning and replication, that from what I can gather have no real competition from other vendors, because they are very stable, fast and feature rich in comparison, which I can attest to. Sure, many other DB's have some implementation of these features, but they are not comparable.
Oracle is very configurable, but also very inconsistent in the syntax for configuration, and everything they provide seems to have followed an organic growth method, rather than an overall encompassing design. A lot of technologies are designed by building on how the underlying engine works. For instance, RAC is constrained by the design of the SGA, rightly or wrongly. DG is constrained by the design of redo log generation. From the very tiny exposure i've had to Postgresql, their design philosophy seems to follow the UNIX/Linux philosophy, and I can imagine that if Oracle had followed suit, then some features in oracle may well have been much more efficient and less complex.
I love working with Oracle DB but then again, im a bit of an elitist, so it appeals to me. I do however get the feeling that it could be a hell of a lot less complex and still fulfill the same goals. And I know for a fact that many Oracle customers don't really need that level of complexity. They could have functioned just fine on any other DB motor, especially the ones that don't use licensable features of oracle, but marketing has lead many to believe it's the only choice if your serious about your data.