Cost
Oracle ain't cheap. At least before you consider costs of porting, programmer availability, etc, etc. Remember, you will almost certainly need a full-time DBA. Good DBA's are not cheap, but are worth their weight in gold. You will also need training for programmers and DBA's. Again, not cheap, but shop around - both for the cost of the courses and for the content.
Oracle are not the only people who give Oracle training, and often a smaller consultancy can tailor a course for your needs and still be cheaper per training hour per person.
If you are getting an application from a VAR, the Oracle components can often be obtained at a good price.
Oracle is not (currently) as object-oriented as some of the competition.
Implementation
Implementation on some systems betrays the heritage of the system it was developed on (e.g. Mail REEKS of VMS) and can be counter-intuitive to programmers used to their (non VMS or non UNIX) OS. On some systems, performance is not what you would (or were led to) expect, so you may need to upgrade your system. (The moral of this story is use systems that are inexpensively scalable). Joel notes particularly that IBM 9370 implementation is slow. (Hey, so is that news to us UNIX types?)
While quite a few people have commented on buggy code,
poor implementation, different keystrokes for different hardware, etc (all
of which have some justification), this is in my opinion generally a bit
harsh. Sure, when comparing Oracle to more single minded systems such as
a compiler or programmer tool, Oracle comes of poorly in quality.
But, remember you are talking about a large system and
compare Oracle to other RDBMS systems and you'll find it actually isn't
too bad. Just make sure the DBA runs each new release in a spare
area for a while ...
Version
Version control of "source" for your applications in some products is painful where you do not have editable ASCII files.
Version changes can give you nasty surprises. OK, so this affects everyone, but there have been a few "patches from hell". (Ask any VMS DBA who applied V6_36 or thereabouts). Personally I generally start feeling comfortable around Vx.0.15 but much prefer Vx.1).
Conclusion
Historically, sales staff were more prone to hyperbolae
than your garden variety marketroid and technical support was poor. This
has improved. Still, installation and upgrade scripts have copped
a *lot* of flack in the newsgroup and I must admit to requiring a second
pass at this sort of stuff, with a decent browse (and hack) through the
install scripts in the meantime. Just as well I had disk and time to spare
that weekend... Also, there has been quite a bit of criticism, at
least here in Oz, of the way Oracle do not inform you about important patches
to the RDBMS until you ring support
with a problem...meanwhile your data just got corrupted.
Apply pressure to your support representative to improve the situation.
