There are several differences when making a cash offer. In addition to showing proof that you have the funds to close you will not be required to meet certain conditions that a bank requires such as an appraisal, which you may wish to purchase unless you are positive that the homes value is correct. You will also not be required to purchase a "lenders" title insurance policy. In most cases the closing period for cash offers is shorter since you do not have to wait for the bank to process the loan. Typically in most cash offers the Earnest Money requirement is also higher.
One thing that a cash buyer must do is to be diligent in their investigation of the property. You must be sure of the value, be sure of the condition and be sure that you are making a good investment. One thing about getting a mortgage is that it provides an uneducated buyer something of a safety net. The bank will not risk it's money if they feel that the property is not a worthwhile investment. Cash buyers do not have that safety net so they need to be prepared.
On the positive side, a cash offer is always more attractive to the seller so you may be able to negotiate a little harder with a cash offer.... more