If I root the device can I upgrade to Froyo without waiting for the operator's release? I have a Samsung Galaxy S and am currently waiting indefinitely for the operator to pull its finger out and release its bloated edition of Froyo.

If I root the device using the instructions here, will that enable me to ugrade to Froyo over Kies or will I have to upgrade through some other method?
Looking at your profile it looks like you're based in the UK? If so you should have no problem running the Samsung's European JPO release of the Galaxy S Froyo software that went out to unbranded UK Galaxy S's a few weeks ago. As this is an Official Samsung release there's no need to root to apply it, you just need to trick Samsung's software into installing it for you.

To start with I'll make the assumption that you have no problems running the Kies software, that it recognizes your phone when you plug it in, and that you get a "You are already running the latest release" message when you click the Firmware Upgrade link. (this is a big set of assumptions given the quality of Kies, if any of these aren't true, then you need to get Kies working properly before going further).

This post on Vodafone UK's Galaxy S forums lays out the steps Samsung Galaxy S - Froyo Update (Android 2.2) (reply 113). I'll summarise them below as Vodafone are about to upgrade their forums to new software, so I have no idea if the post will survive, or the link will still work in a week or two's time, credit to "ado28" for these instructions.


  First of all you need to go into
  regedit and do some minor alterations
  to the registry.
  
  Do not update Kies! If you do then I
  think this tweak won’t work! The Kies
  version I used was 1.5.0.10024_74 but
  I fooled it into thinking it was the
  latest version 
  
  Step by step guide
  
  
  Back up everything you wish to keep, including Apps, phone numbers,
  Text messages etc because we're going
  to wipe your phone clean before we
  start!
  Go to Settings – Privacy – FACTORY DATA RESET and click. Follow the
  prompts and then let it wipe your
  phone.
  Now you have a bare naked phone again and can proceed onto the next
  step.
  Open up Kies and leave running
  Connect phone
  Open Regedit by clicking on Start – Run – then type in regedit and press
  enter
  Scroll down to Kies and look for “Localver” see pic
  Change your Localver code to 1.5.3.10103.100
  Now go to your Device DB folder and change your settings to these:
  
  
  "SoftwareRevision"="I9000XXJF3/I9000OXAJF3/I9000XXJF3/I9000XXJF3"
  "ProductCode"="GT-I9000HKDXEU"
  "HIDSWVER"="I9000XXJF3/I9000OXAJF3/I9000XXJF3/I9000XXJF3"
  "DEVCONINFO"="" Delete the writing
  in this box and leave blank.
  
  
  Now go back into Kies and click "Update firmware"
  
  
  This will now allow everyone who has
  JPA on their handset with the product
  code XEE to be replaced with JPO and
  the product code XEU which is for the
  UK. Once you have successfully updated
  then allow the phone to boot up. Once
  booted up you will now need to go back
  into your settings and change your
  product code to XEU. To do this open
  your keypad and type in *#272*YOUR
  IMEI# and now you will be back to
  having a lovely wee choice of product
  codes to enter. Choose XEU and
  install. The phone will reboot and you
  will now officially be on JPO with the
  correct product code XEU!
  
  Please note that by doing any update
  on your phone could cause it to brick
  itself. The guide I have written
  worked perfect for me however I can’t
  be held responsible if your phone
  bricks itself. To be safe always try
  the 3 button recovery method first
  before you update and also doing a
  factory reset first usually ensures a
  smooth installation of new firmware.


Extra note on Kies: as stated above, this doesn't work with the latest version of Kies. If you need an older version of Kies then this version should allow you to do this (according to XDA): Kies version 1.5.3.10093_82.

If you do end up uninstalling and reinstalling Kies and find that it doesn't detect your phone any more, then first thing to try is clicking the menu icon in the top-left corner of Kies and selecting the "install drivers" option.