There have been dozens of threads about why the change was necessary and how to navigate it. You can try reading some of those. The main point is that TB runs on software from an outside vendor, the old software was obsolete and could no longer be protected against security breaches and such, and will be losing its functionality.
Ads are an issue periodically. TB is a business and ads are one of its revenue sources; they help to keep supporting membership costs down and let the forum be available at all to non-paying members. One of the benefits of supporting membership is that it reduces the ads you're exposed to, but periodically when there's a change in the software things get glitchy and people get ads they shouldn't. This has happened before, it's part of the process, and Paul works it out with the vendors until all the permissions and blockers get settings so the site works as intended.
As far as finding the forum of your choice, so far for me, the most useful thing has been the "Forums" tab at the top of my screen and particularly the drop menu you get when you click the arrow next to it. In Firefox and Chrome, at least, that's giving me this, which, you'll notice, let's me access all the new posts, or pick a particular forum from a list, or do searches or check my watch list, etc.:
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Having said that, there are still parts of the transition ongoing, especially in the classifieds, and personally I'm not seeing "hot deals" available right now. I suspect it will come back once everything is complete.
