Well the (ARM) tablet's I would consider are:

Budget
$180 - The Superpad2
$200 - Nook Colour
$210 - Herotab C8
$300 - Original Galaxy Tab

Mid-Class
$320 - Advent Vega/Viewsonic G-tablet (my favourite)
$450 - LG G-Slate
$500 - ASUS Transformer 16GB Wifi
$500 - Apple iPad (needs no introduction)

High-End
$550 - RIM PlayBook
$600 - iPad 2 (double the capability of the original)
$600 - New Galaxy Tab (8.9" / 10.1")