So far, no errata.
The approach to verbal aspect that I expound here owes most to Mari Olsen, whose work on verbal aspect differs from that of Porter, McKay, and Fanning; her work frequently comes up on the Biblical Greek mailing list.
On the whole subject of verbal aspect, see:
Fanning, Buist. Verbal Aspect in New Testament Greek.
Oxford, 1993?
Fanning and Porter brought verbal aspect to the fore in recent
grammatical studies on New Testament Greek.
McKay, K. L. A New Syntax of the Verb in NT Greek. Peter
Lang, 1994.
A valuable discussion of verbal aspect from a scholar trained
in classical Greek. He has several noteworthy articles in scholarly
journals as well.
Olsen, Mari Broman. A Semantic and Pragmatic Model of Lexical
and Grammatical Aspect. Garland, 1997.
A dense treatise on verbal aspect that sketches the approach that
looks soundest to me.
Porter, Stanley. Idioms of the Greek New Testament. Sheffield,
1992.
This is Porter's update of C. F. D. Moule's Idiom-Book.
Porter, Stanley. Verbal Aspect in the Greek of the New Testament.
Peter Lang, 1993.
Porter's entry in the verbal-aspect argument.
Carson, D. A., and Porter, Stanley, ed. Biblical Greek Language
and Linguistics. Sheffield, 1993.
A collection of essays, including a readable argument between
Fanning and Porter with commentary from several respected scholars.
(Olsen's position is not represented.)
Greek-to-English Exercises
1 I am leading
2 They are saying
3 I am teaching
4 Y'all are writing
5 They know
6 You are finding
7 they believe
8 he/she/it sees
9 we believe
10 he/she/it has
11 we see
12 you are releasing
13 he/she/it is saying
14 they are receiving
15 y'all hear
16 we have
17 y'all are receiving
18 you hear
19 he/she/it is finding
20 we are leading
21 you have
22 I am writing
23 I am releasing
24 y'all are teaching
25 I am teaching and writing, but I do not believe.
26 You see and y'all hear, but they know.
27 Is he/she/it leading and finding?
28 They are receiving and they are not releasing.