Rather than replacing your exterior with the same old knob, lever, or handleset, consider instead replacing with newer secure Keypad Entry or Electronic Entry.

Keyless entry: Keyless entry deadbolts come with alpha numeric keypads.  With a Keyless Entry you do not need to worry about someone stealing your keys.  No more fumbling around for keys in the dark. With an illuminated keypad entry, you punch in your own preset 4 digit code.  There are no more keys to carry with you. Just lock and go.  This brings a new level of security, with the option of over 10,000 different code combinations.  Keyless entry systems are also known as mechanical systems, since they do not rely on a battery; they are also hacksaw proof and pick proof for even greater security.
Keyless entry is also ideal for people with disabilities, for they can easily access the keypad.  They are also great for the blind, for they can put in their chosen code by their ability to feel the keypad and punch in their code number.
Electronic Entry: Powered with a 9 volt battery that lasts for up to 3 years, your lock opens by way of an electronic signal.  Electronic Locks usually come with more features, such as locking automatically shortly after entering home, while still being able to exit as needed.    
Electronic entry locks can also be purchased with a flexible lock that will stay locked or unlocked whichever you choose, simply turn a thumb turn lever to keep locked or unlocked.   
Any of the above mentioned locksets can usually be used to replace current locks.  They are also easy to install, normally within 30mins.  Installment of your new Electronic Deadbolt Entry is easy.  No wiring needed.  Simply install using a flat head and Phillips head screwdriver..