I'd consider them higher cost / same quality right now. I don't recall having an Asus product ever fail on me, but I haven't had many products from other companies fail on me either.
Things are changing. Compare user reviews on newegg from Z87 to Z97; the number of (one egg) negative reviews is up 50% or better. The Rampage Extreme IV (I have 2 of the older models) has more warranty fails as a % of units sold than any other board on the market
http://www.hardware.fr/articles/927-2/cartes-meres.html
Failure rates > 2 % (Asus 10, AsRock 7, MSI 3, Ggabyte 1)
- 8,80% ASUS Rampage IV Extreme
- 8,05% ASRock AD2550B-ITX
- 7,93% ASRock FM2A88M Extreme4+
- 7,25% ASRock 970 Extreme3 R2.0
- 7,20% ASUS Maximus VI Extreme
- 5,95% ASRock 970 Pro3 R2.0
- 5,93% MSI Z87I
- 5,56% Gigabyte GA-990XA-UD3
- 5,26% ASRock 990FX Extreme3
- 5,06% ASUS Maximus VI Formula
- 5,05% ASRock FM2A55M-VG
- 4,76% ASUS Z87I-PRO
- 4,55% ASRock Fatal1ty Z87 Killer
- 4,42% ASUS Maximus VI Gene
- 4,26% ASUS Z87-PRO
- 4,13% ASUS SABERTOOTH Z87
- 3,65% MSI Z87-G45 GAMING
- 3,48% MSI Z87-G43 GAMING
- 3,37% ASUS Z87-A
- 3,29% ASUS Z87-K
- 2,17% ASUS Z87-PLUS