[update]

I've been using the 3B+ as a media server for a year now. Omxplayer handles 1080p (even m2ts files) easily. Truly amazing what can be had for $35. My Pi replaced an $800 fujitsu laptop and I haven't noticed a single bit of difference in performance.

[candiodari]

Do things like mkv files work ?

[captn3m0]

Everything but x265 or 4k

[gwilliams]

Yes.

[senectus1]

same, though i wish they'd make one capable of playing 10 bit video encoding.