The Shepherd of Hermas was very popular and highly regarded in some circles in the early period.
a) it is present in Codex Sinaiticus (the British Library portion, after the Epistle of Barnabas, includes the Shepherd of Hermas up to Mandate iv.3.6; among the 'New Finds' at St Catherine’s Monastery there are Parables 6, 8.1–2; 9.xiv–xvi, xviii; Visions 1–5; Commands 1–4)
b) it was generally popular (e.g. Irenaeus quoted from it in Adv. Haer. II.xxx.9 and even designated it as "Scripture" in IV.xx.2)
c) Hermas is extant in 21 papyri (acc LDAB; Sept 2008), including ten from Oxyrhynchus, four of which were clearly substantial judging by the surviving pagination: P. Oxy 404 (III/IV); P. Oxy 1172 & 3526 (IV; page 71); P. Oxy 1599 (IV; page 73); P. Oxy 1783 (IV); P. Oxy 1828 (III); P. Oxy 3527 (III; page 83); P. Oxy 3528 (II/III; page 119); P. Oxy 4705 (III); P. Oxy 4706 (II); P. Oxy 4707 (III).
Of the others some early and substantial manuscripts include: P. Iand. I.4 (II/III); P. Mich 2.2 130 (III); P. Mich 2.2 129 (III; 31 folios); P. Berlin 5513 (III/IV); P. Bodmer 38 (IV/V; 22 folios).
In terms of manuscript attestation and patristic appreciation the evidence looks better than large parts of the New Testament.