Aphex Twin isn't mainstream in the SLIGHTEST, and is definitely not accessible. Aphex Twin is a pioneer in the electronica/IDM field, and one of the most important modern artists around. People like him because his body of work is consistently great - everything from Selected Ambient Works to Drukqs. I would greatly recommend Aphex Twin because of this.
And generally the people who like Aphex Twin ARE those who have heard a great deal of electronica.
And Tiesto is garbage
btw I'll also recommend everything on Warp Records, especially Jackson and his Computer Band.
I agree with pretty much everything in this post - although supposedly Drukqs was kind of a sell-out album, something about pre-empting an internet leak of 50240492402 tracks from an MP3 player he lost (I would like to hear those tracks though)
You can tell the material on Drukqs wasn't meant to be together in an album at all. Besides the obvious Piano tracks vs. super-fast electronic seizure tracks, Bit 4 sounds like it was made at the same time as "Bit" from the Hangable Auto Bulb EP (like maybe he made a whole bunch of "bits" at the same time and picked the one he liked best), and bbydhyonchord sounds a lot like the beat from Mookid along with the ptzzty sounds from I Care Because You Do in general. And Gwely Mernans could easily be one of the "non-selected" Ambient Works from Volume II. Like just imagine it with a name like DOORKNOB or something.
Even though Come To Daddy was one of his most mainstream head-bangin' thingies, I would seriously recommend the single as an introduction to Aphex because it has so much variety in the other songs. Film and IZ-US are so beautiful and fragile it's kind of hard to comprehend it was made by the guy who did the title track. And Bucephalus Bouncing Ball is just so frenetic while being mellow at the same time. (And supposedly it was made out of all different samples of bouncing balls and marbles and stuff) The other tracks are a lot WEIRDER to say the least but I was surprised how solid they were musically, most of the time anyway.
But definitely don't listen to Selected Ambient Works Vol. II first. It pretty much DEFINES inaccessible, and there are tracks I still haven't been able to listen all the way through because half of the tracks are like a dream and the other half is like the worst nightmare you could possibly have. But Selected Ambient Works 85-92 is very easy to get into although the SUPERBASS kind of gets on my nerves sometimes. I wish he'd reissue it with a better mix and stuff but then again I probably wouldn't want to buy it all over again.