Is the market filtering the same as a phone (auto detects required features and OS version) or do developers need to specifically set attributes on their apps for them to be available on tablets running Android?
From what I read a few days ago, tablet cannot run Android Market (and therefore will not be distributed with it) until 2.3 is released in the early part of next year. I have heard of a few tablets being released using the manufacturers own market-type application but nothing using the official Android Market.
I think we'll have to wait until 2.3 is released before we hear about tablet support =(
Since the answer from gsteinert is a little bit outdated, I will try to give an update:
Apps on tablet will go to the same filter process as apps on phones on the Market.
Apps that appear on tablets follow the same filtering rules as with phones. Developers are given the ability to set attributes for their app in the, so called, manifest. For example: If an app declares that it's, for whatsoever reason, only compatible with small screen sizes, it will not show up on the Market on a tablet with greater screen sizes. Note that this case is very rare, because most apps that are only designed for small screens will either be upscaled or just use a small amount of the screen.
There is also a way to declare an app for honeycomb tablets only.
Again an update, as meanwhile Flow's answer also got a little outdated (LOL):
On the other hand, Google started to work on this issue meanwhile. So you find a tab titled Featured Apps for Tablets at least on the Google Play website. For details on this, you might also wish to read Google Play tablet apps getting special designation; according to that article, the Google Play Store is now only showing tablet-optimized apps in its top lists when accessed through a tablet.