I've just recently switched from a Palm Treo to an iPhone. I love most everything about the iPhone but am disappointed in it's search capabilities. When searching Contacts, the only fields that are searched are first and last name. On the Palm you could search all fields in Contacts and in Memos the search function searched the entire content of all Memos.
I had over 1400 contacts and a large number of memos on the Palm Treo. I exported/imported the Palm Memos to the iPhone in vCard format. This worked well, but I could still only search by Name field.
What I did to solve the problem of expanding search was load the vCard export from the Palm Treo into Stanza, an ebook read for the iPhone/Touch. Then I imported the resulting 'ebook' into the iPhone. Now I can search the 'ebook' version of my contact data completely (all fields) and very quickly.
I did the same with all my Palm memos. Exported them as a single file from Palm Desktop, imported them into Stanza (which turns the file into an ebook), transferred the 'ebook' to the iPhone, and then the memos are easily searched. The search hits are nicely highlighted by Stanza.
One could export the iPhone Contacts via iTunes in vCard format, import the file into Stanza and then, from within Stanza on the iPhone/Touch have the entire content of the iPhone Contacts data become nicely searchable. Stanza searches quickly and give you a list of all the hits from your search target.
You'd need to check out the Stanza website regarding the method for getting text files into stanza on your computer and then getting them into your iPhone/Touch. It's not too difficult. I'll explain it if anyone is interested.