Welcome to bugzilla doesn't give people information about the bugzilla they're using
This is part one of probably 10 or 20.

I'm a bugzilla 2.10 user. I've always been a bugzilla 2.10 user.

What makes me a bugzilla 2.10 user? It's the bugzilla i was using when i first started using bugzilla.

Hopefully by now I know all about the bugzilla 2.10 features.
Unfortunately every now and then people upgrade the bugzillas I use.

I've never gotten an email from bugzilla-daemon or bugzilla-admin-daemon or bugzilla-upgrade-daemon telling me "hey, we just upgraded, and as a user of bugzilla, here are some new features that you can take advantage of".

As it happens, as a regular on irc.mozilla.org and various channels in it, I tend to have some theoretical idea of what those new features are, but as a real normal user, which is a hat I wear often enough on a dozen bugzillas, I have no idea what features the upgrade gave me or when bugzilla upgraded.

steps to reproduce:
1. create an account at a bugzilla
 A. telling it the version of bugzilla that you understand (if it won't let you tell it what version you know, or if you don't know bugzilla, leave it blank and let it assume you've never met bugzilla)
 B. telling it what you are going to use bugzilla for (the default is "to report a bug, silly")
 C. possibly telling it my tolerance for new hints (default tolerance of about 10, other numbers include "I'm a bookworm, tell me everything", "5", "2", "tip of the day, one please", "I'll figure it out on my own")
2. get an email from bugzilla with your new account information (basically a password)
3. read the email for all the other important information, like a list of important new features added since the bugzilla you were familiar with.

Note about 3. If I say I've never met bugzilla, unless I say that I'm a bookworm, I should not be told about all features in bugzilla 2.22, i should be told about the basic important features of bugzilla 2.10, after a certain number of logins (by me to bugzilla) or bugmails (sent by bugzilla to me), i should get another email telling me about important new features in the next lump (either version at a time, or up to the tolerance I specified).

4. use bugzilla for a while
5. eventually without knowing it, someone will upgrade bugzilla
6. keep using bugzilla exactly the same way you used the bugzilla from before it upgraded, because bugzilla hasn't told you about new features, and it certainly hasn't done a good job of explaining new features to you.

Expected results, basic overview:
1. new account page should offer:
Login Name:
[                                                            ]
Real Name:
[                                                            ]

[ Create My Account Already ]

To better tailor your user experience you can provide these optional details:
I intend to use bugzilla to:
[ Report a bug, silly                             |v]
  Get support
  Provide support
  Provide a fix
  Do my job, it's complicated
  Get managerial reports

I'm familiar with a bugzilla that was current in:
[ None, I've never used bugzilla before|v]
  2006, Bugzilla 2.22
  {year it became common}, Bugzilla 2.20
  ...
  {year it became common}, Bugzilla 2.12
  {year it became common}, Bugzilla 2.10
  Before it was publicly available, Bugzilla 1

Bugzilla will provide explanations of new features.
Tell me:
[ Just the basics                                 |v]
  I'm a bookworm, tell me everything
  Up to 10 new things at a time, don't overload me
  a couple of things, but I'm really busy
  Tip of the day, one please
  I'll figure it out on my own  

Explanation of order, we're *always* favoring end users, so their option goes first. average users just want to report a bug and haven't used bugzilla before. Expert users can get used to selecting something from a list. Managers are going to need things to stand out, so their slot should be last.

The bugzilla versions are basically newbie and then most recent through oldest. If someone remembers using bugzilla a long time ago, it's then easy for them to jump to the end. if someone was using

Note: the Bugzilla 2.22 line should change from 2006 to 2007 when we reach 2007, because at present it's uncommon to actually find 2.22 in 2006, but the year listed should never be a future year. It's OK for the year to be unstable as bugzillas upgrade, because in general, no user should actually see this very often, and a single year jitter will not hurt their experience  (they'll think it's a fluke if they actually remember).

Note: unfortunately, if a user selects "manager" in the role and has js enabled, then all the witicisms (e.g. I'm a bookworm  and Before it was publicly available) should be replaced by if you're pardon the expression, witless raw numbers.

2. new account email should have some basic suggestions about what you can do with bugzilla *based on what you tell it*

detail:
if you say report a bug, 2.10, and don't say bookworm, then the email will basically explain how to use bugzilla to search for bugs, how to read about products, their descriptions and report a bug.

Note the order. Search first, then introductions to products and descriptions, last report bugs.

if you say bugzilla 2.20