I thought it might be useful to some people to summarise my impressions and opinions of these wine auctioneers.

Feature Gray's Langton's
City Base Sydney Sydney and Melbourne
Online Site Basic, but it works.  No sales history available except for your own wins / losses. The best!  Good facilities and resources for buyers, price history etc.
Auction schedule(s) Many auctions every day, some for one day only, some for longer periods. Fortnightly Melbourne/Sydney auctions, one on at all times, now weekly.  Wine Exchange open for fixed-price lots, free of commission in January each year.
Bidding $5 increments, per lot bidding $1 increments, per bottle bidding
Auction close-off 10 minutes after the last bid on an item. Promptly at scheduled time
Buying/Selling Charges Buyer's commission 15%, sellers commission ???. Buyer's commission 15%, sellers commission negotiable from 15% down.
Freight Varies by location, quite expensive for 6-packs, no consolidation $16.50/case Australia-wide
Pick-up allowed No Yes
Insurance Not mentioned. 1.5%, minimum $11 (optional, but cannot opt out online, have to ask for a refund)
Delivery time Within 1 week Varies, Exchange within 1 week, auctions can be slow.
Communication Slow at times, improved with the new customer service system Good.
Returns On regular "auctions", if faulty or mis-described, 30 day guarantee.  Refund of total including freight.  For cheaper lots they don't even want the wine back. Generally no, unless whole batch appears faulty or mis-described.
Terms of sale Title passes on payment and delivery. Title passes on sale at end of auction.
Delivered cost of one $300 lot (ACT) $300 + $45 + $17 = $362 $300 + $45 + $16.50 + $11 = $372.50  or $361.50 without insurance

For those who have been or are thinking of bidding on Gray's Online wine auctions, this article may be of some interest.  It documents my experiences with Gray's wine auctions over the last nearly 12 months.

Feature Cracka Wickman
City Base Sydney Adelaide
Online Site Has Dutch Auctions with countdown time and a fixed-price Wine Market.  Nice look, but can be a bit slow and the Wine Market "Reveal next 20" presentation is not to my liking.  No sale history, even for your own purchases. Basic, but it works.  No auction sales history available.
Auction schedule(s) One daily, all new product, no secondary market sales.  Mixed-case Mondays, cheap-and-cheerful Tuesdays.  Currently 10 or less wines/mixes offered per day. Monthly
Bidding

50c increments, per bottle prices, Dutch auction, price reduces from RRP to sale price, lots often go at or near the minimum bid price, except for the occasional offering that generates some demand and competitive bidding.  Fixed price Wine Market offerings are often available more cheaply elsewhere, especially after freight is added, but there are some good buys there at times.

 $1 increment pb bidding
Auction close-off When all sold or minimum price reached without sale. Promptly at scheduled time
Buying/Selling Charges Buyer's commission 0%. Buyer's commission 10%, sellers commission negotiable.
Freight Auction buys fixed price per destiation, Market buys varies significantly, but can be high for 6-packs especially. 1 Bottle $10, 1 case $15 to most of Australia if value of sale exceeds $250, otherwise a $15 surcharge.
Pick-up allowed Not normally Yes
Insurance Included in freight charge. 1.5% if value exceeds $240
Delivery time Generally very quick Up to 21 days.
Communication Good, responses by phone or email. Good
Returns Accepted if wine faulty or doesn't match description. ???
Terms of sale    
Delivered cost of one $300 lot (ACT) $300 + $14.95 = $314.95 $300 + $30 + $15 + $4.95 = $349.95

 

Feature Oddbins  
City Base Adelaide  
Online Site Very basic, silent bid, nominate your top price and that's it. No auction sales history available.  No Online payment facilities or account management.  Invoice by email 2 days after auction close.  
Auction schedule(s) Frequent  
Bidding Varies, they suggest increments depending on anticipated cost per bottle.  
Auction close-off Promptly at scheduled time.  
Buying/Selling Charges Buyer's commission 15%, sellers commission ??.  
Freight Fixed $13.50/carton, + mandatory insurance @ $2/$100  
Pick-up allowed Yes.  
Insurance Added to freight charge.  
Delivery time    
Communication ?  
Returns Auction terms exclude any liability for quality, mis-description etc.  
Terms of sale Risk passes at close of auction, terms of sale exclude any comeback for any errors etc.  
Delivered cost of one $300 lot (ACT) $300 + $45 + $13.50 + $6 = $364.50  

If you have had dealings with other wine auction houses, I'd be happy to publish your impressions here if you send me the information covering the same factors I've used above.