Visible 2.0 features include:

A tab menu in the menu bar for configuring your tabs
An activity and log viewer (rudimentary right now)
A parameter for both running on a USB drive, and multiple users
A light freshening of the UI through new icons and other small changes
Links to related web tools (forums, for example)
Platform-specific features (Installer on Windows, new UI library on OS X)
There's a 'Test Login' button on the eBay configuration tab!
A clear indicator of current login status in the toolbar
A thumbnail column
Indian Rupee support
Much better parsing, including fixes for most major current problems
A few of the things fixed since the first alpha:

Per-item events should be preserved between runs
Comments and 'valid' status should be preserved between runs
Always focus on the text field when for the 'Add Auction' dialog
A better icon indicating there was a problem loading an item
Recognize 'button' tags as input tags, improving login consistency
Thumbnails are being loaded
'Report Bug' goes to the Lighthouse page now
The eBay server menu is back
better non-English character support
preserving the currency of items correctly between runs
remembering snipes between runs
retrieving and displaying shipping and location information
recognize deleted items versus items that we're having network trouble loading
recognizing the latest 'image not present' thumbnail
fixing the 'Buy' operation
supporting Indian Rupees
preserve last bid and last bid quantity between runs
visibly sort tables correctly on first display so the rows aren't in an inconsistent state
sped up 'shut down' for large auction collections
fix column headers which had been broken by a well-intentioned fix for Vista
Under the hood:

I've added a database where all auction information is stored
There's scripting support, waiting to be used
The source code has been heavily refactored for easier development
If you set 'logging.remote' to 'true' in the advanced config, it'll report exceptions to my server directly.
Things that are still not quite right:

No UI for enabling exception logging to my server (for debugging)
Minimum bids on Dutch/Power Auction listings are off a little
The Custom Columns popup menu sometimes doesn't pop up (especially after an upgrade)
Log viewing doesn't refresh
Sniping repeatedly retries if the bid is below what eBay accepts
Deleting a large number of items at once might raise a higher CPU load than usual
Vista's column headers look terrible
Some of the internal changes from 1.x (the addition of the database and scripting, mainly) add libraries that make the program substantially larger, so the downloads might take a little longer

Scripting and log viewing are both rudimentary right now, but provide a placeholder for future improvement.

There are features that have not yet made it into the 2.0 beta, but I want to get new releases out so folks can test the changes that have been made.

fixing a slew of eBay breakages over the last 3 weeks.

Correctly recognize the 'outbid' page when the existing hidden proxy bid is above your bid (the text was changed).
JBidwatcher is smarter about some character set functions, so you don't see as many '?' in browsing eBay items through its internal webserver.
Fix PayPal recognition.
Recognize the 'safe trading tips' interstitial, and some forms of the 'you don't meet a requirement' page, if it's possible to continue.
Both of these will slow down bidding, so if the snipe timing is set too close, JBidwatcher may not have enough time to handle these pages and still bid in time.
Fix the internal webserver's display list to show the snipe when one is set.
Removed older 'Buy It Now' detection code, as it was causing failures to load items.
(It still recognizes BIN items, the old code was from one of eBay's many wording changeovers.)
Improve Currency handling to avoid many of the problems which have caused the UI to lose all columns but 'Ended Date'.
Fixed up error messages somewhat.
Added an entirely optional setting for users to enable an 'Affiliate mode' where the author can make a few nickels at no cost to users when they 'browse to' an item that they later end up winning/buying.
Better recognition of the existence of a captcha (ebay's increased security graphic).
Fix potential negative bid counts.
Fixing US prices in the auction info, and better recognize them so we can estimate the sum of items in multiple currencies.
Some FAQ improvements, including a whole new FAQ on the site, that is distinct from the one in the program.
There are now forums, available at http://forum.jbidwatcher.com!