There have been a couple threads on pagination here in the last couple weeks. I personally don't like pagination. Here is what I like to do instead for a category of widgets with a couple hundred products in it:
1) Remove pagination entirely, 301 redirect pages 2 and greater back to page 1.
2) Create category filters. Allow users to apply combinations of filters using AJAX. Create crawl-able pages for key individual filters. Base the crawl-able filter pages on which are important to users, which have search volume according to adwords keyword suggestion tool, and which get the range of widgets well represented between the pages. For example:
Brand X Widgets
Brand Y Widgets
Feature A Widgets
Feature B Widgets
Red Widgets
Blue Widgets
Budget Widgets
Luxury Widgets
3) Link each product to other related products. This passes pagerank around much more efficiently than pagination. There are lots of ways to do this.
People who viewed this widget also viewed...
Other widgets by the same brand...
Other widgets with the same feature..
Advantages of pagination:
* Easy to implement
* Gets everything crawled and indexed
Disadvantages of pagination:
* Not typically used by users
* Not good at passing pagerank to products beyond page 1
* Creates many category pages with duplicate or similar titles
* Pagination pages actually use up some pagerank that you would rather have on keyword targeted pages.
Your "show all" page can be good if you don't have too many products on it and you don't show too much information about each product. I'd try to keep the page size to 2MB and ensure that the top of the page starts rendering before the entire page is downloaded (if more than 100 products). I had a competitor with a page with 2000 products on it. It takes a little while to download, but users that do wait for it get a great experience. My competitor implemented javascript filtering of the products on the page. Filtering and drilling down to the product you want is zippy fast.
Other recent threads on pagination to check out:
Canonical and duplicate content from pagination [webmasterworld.com]
Canonical URL tags and INDEX on Pagination? [webmasterworld.com]