I've had my R3000 since November of 2012.
Its a very reliable printer and i use it about weekly for small canvas prints. The roller feed on the back of the machine works very well for canvas and is only limited by its need for 2" cores. The Epson exhibition canvas recommended by OEM for the 3000 is very stiff to work with when it comes to stretching canvas, it has about 23mil thickness if i remember right. I much prefer the 18mil thickness of the PremierART Generation canvas i found at Altex in Chicago - very nice people to deal with by the way. I've so far bought 9 20-foot rolls of the canvas.
I would not be happy with the expense of OEM ink cartridges for the R3000 if i went that way. I went with Cone inks from inkjetmall and get 4 refills for the price of one OEM cartridge. I've had no clogging problems because of the switch and furthermore, the Cone inks website, inkjetmall, tells one how to do cleaning of the epson printing head exterior, wiper assembly, and parking area, information that is not available on the Epson site. I've had to do that once and it worked great.
If i had to do it over again, i might well go with the 3880 because of the greater size capability, i.e. 17".
But I think i would miss the roller feed, the WIFI convenience, and the R3000 reliability.
best of luck, they are both great machines, phil