Hello vicky. IE has a default length of 2084 characters I believe. Keep in mind that it is not the length that is the determining factor but how many clicks it takes to get to what resides at the end of that long URI.

From a visual standpoint, shorter is better. Remember too that URIs wrap in emails and are typically broken when this happens and that is why shorter is better.

Believe me, stay away from the long URIs as much as possible. They can be a bear to work with especially when they reach the wrapping point.

In reference to URI character limits, once you've reached that limit you will get the rare 414 Status Code...

10.4.15 414 Request-URI Too Long
The server is refusing to service the request because the Request-URI is longer than the server is willing to interpret. This rare condition is only likely to occur when a client has improperly converted a POST request to a GET request with long query information, when the client has descended into a URI "black hole" of redirection (e.g., a redirected URI prefix that points to a suffix of itself), or when the server is under attack by a client attempting to exploit security holes present in some servers using fixed-length buffers for reading or manipulating the Request-URI.

I say rare because I've never seen a 414 before. :)

you might want to read some of the previous WebmasterWorld discussions about url length.
in particular:
although this thread is about "Max. length of web page title [webmasterworld.com]" it also contains some information about url length.
and here's a thread about seo and url length -
"Is URL Length a Ranking Factor - what say you? [webmasterworld.com]"