i use one because i'm left handed and i'm cool.
if you have a intelli optical and you can't identify it, do a search for the first part of the p/n, some site, might be a sales site with technical stuff about it will show up telling you weather its a 1.1 or 1.1a
p/n x08-70385 pid 55250-576-4296167-0
search for x08-70385 part
lol out of the seven mice i have, two can be easily identifyed 1.1a and 1.0
, three of the remaining i found out were 1.1a's, and the last two were both 1.1's but only one worked lol 
.1.1 uses same sensor as intelli 3,
1.1a uses same sensor as intelli 4 ,
YOU WANT 1.1
the below link has great info about different sensors used in various mice.
http://home.comcast.net/~richardlowens/OpticalMouse/
btw if you dont try teflon feet for this mouse, you're really missing out
it makes a massive difference .do it yourself teflon feet
come in strips of two from any hardware place, bit tricky to shape and get the right height, you need just a very thin layer of rubber backing left, just a tad higher than original feet, use old mouse feet as template to cut around, sharp stanley knife, scalpal would probably be better though, or maybe one of those hobby knives, sandpaper needed to finish off shaping and thicknes. well worth the effort
. obviously important to get the backing exactly flat, dont want any nasty hot spots, also i used some bluetack to fill in the screw holes under the back feet.put the strips in the freezer overnight, makes the rubber easier to cut
another essential thing to do is to get it running at 500hz, try this,
http://www.majorgeeks.com/USB_Mouserate ... d4469.html
to find out what rate your mouse is running at, download this little thingy
http://www.cybergamer.com.au/files/773/
oh btw im now 100 percent sure i'm using a 1.1 with brand new teflon feet lol .
a bit about pads, no not the feminine type sickos,
i've been playing for errr i forget, has to be over 10 years now though, yes and i'm still crap
lol, but hey i'm a sexy guy, that you can't deny,anyway i've never used a pro pad, nor have i experimented with different fabrics, but i have experimented with a massive amount of hard surfaces, glass, plastics, ceramic tiles, marble, granite, etc etc, all with different textures.
personaly and using teflon mouse feet i've found plastic works best, quieter than glass, mouse feet will last longer, nice and slippery.
i'm using a black cutting board which you can get from kmart, they come in packs of three of different sizes and colours, black one being the largest, has a very fine texture, the plastics quite soft so easy to shape, i even rubbed fine sandpaper marks out using my thumb
oh and before using it give it a good hard scrub to remove surface film otherwise mouse feet will turn black lol, rub rub, rub rub rub.
one more thing, buy some round rubber adhesive pads for the mousepad, these are great as they squash down very thinly after some use.
i thank you and goodnight
, and yeah it does