Im not new to modding phones, I modded my old moto razer v3x. (which went thru the washing machine twice and the microwave. AND SURVIVED) But i had to get a new phone after it finally died. I chose the w910i, cause it was the cheapest on 3 (prepaid). Anyway, ive had a look at the modding forums here and dont understand a thing, its way different from moto modding.

So, can some people convince me that its worth my time? Is there anything that can change my mind?

Well it's all up to you, only certain mods actually increase the usability of the phone, most of it is just for looks.
If you find the sound quality poor then you can increase the volume and quality to some extent using different acoustic drivers
If you aren't happy with the camera quality then you may want to change your phones camera driver.
Graphical mods allow you to change the fonts, add extra flash menus to the phone and so on.

and then there's patching that increases the usability.

hmm, you guys have done a good job already. The acoustics on my phone is very "tiny", and the camer doesnt even have zoom in photo mode!

I use mac, which is not the most friendly modding OS, but there were some programs for modding motos for mac. So are there any modding programs for sony ericssons on mac?

p.s i have parallels running on mac, so i can use windows as a last resort.