Thanks for a fun puzzle Mike.
The solution really flowed well with my only real work being to put steps in the right order to simplify my solving path.
Caida, Afmob and I also solved it by similar routes so there appears to be a fairly well defined although not narrow or difficult solving path. Having said that I think there were enough differences for me to also post my walkthrough.
I agree with Afmob's rating of 1.0.
Here is my walkthrough, which is my shortest one for a long time.
Prelims
a) R1C12 = {19/28/37/46}, no 5
b) R3C56 = {14/23}
c) R5C23 = {39/48/57}, no 1,2,6
d) R5C78 = {13}, locked for R5 and N6, clean-up: no 9 in R5C23
e) R7C45 = {14/23}
f) R89C9 = {16/25/34}, no 7,8,9
g) 7(3) cage at R1C6 = {124}, CPE no 1,2,4 in R1C89
h) R567C6 = {389/479/569/578}, no 1,2
i) 19(3) cage at R8C3 = {289/379/469/478/568}, no 1
j) 26(4) cage in N2 = {2789/3689/4589/4679/5678}, no 1
k) 27(4) cage at R2C8 = {3789/4689/5679}, no 1,2
1. 45 rule on R12 1 outie R3C2 = 1 innie R2C8 + 1, no 1,2,3 in R3C2, no 9 in R2C8
2. 45 rule on R89 1 outie R7C8 = 1 innie R8C2 + 1, no 1 in R7C8, no 9 in R8C2
3. 45 rule on N3 2 outies R1C6 + R4C7 = 1 innie R3C9 + 7, max R1C6 + R4C7 = 13 -> max R3C9 = 6
4. 45 rule on C123 2 outies R29C4 = 17 = {89}, locked for C4
4a. 13(3) cage at R1C3 = {139/148/238} (only combinations with 8 or 9) -> R12C3 = {1234}
5. 45 rule on C789 2 outies R18C6 = 3 = {12}, locked for C6, clean-up: no 3,4 in R3C5
5a. Max R1C6 + R4C7 = 11 -> max R3C9 = 4 (step 3)
5b. Min R1C6 + R4C7 = 8 (step 3) -> no 4,5 in R4C7
6. 4 of 7(3) cage locked in R12C7, locked for C7 and N3, clean-up: no 5 in R3C2 (step 1)
7. Naked pair {12} in R1C6 and R3C5, locked for N2
7a. Killer pair 1,2 in R7C45 and R8C6, locked for N8
7. 26(4) cage in N2 = {4679/5678} (cannot be {3689/4589} which clash with R2C4), no 3, 6,7 locked for N2
7a. 3 in N2 locked in R3C46, locked for R3
8. Naked triple {124} in R12C7 + R3C9, locked for N3
8a. Naked pair {12} in R3C59, locked for R3
9. Max R3C9 = 2 -> max R1C6 + R4C7 = 9 (step 3), no 9 in R4C7
10. 27(4) cage at R2C8 = {3789/5679}, 9 locked in R3C78, locked for R3 and N3, clean-up: no 8 in R2C8 (step 1)
11. 18(3) cage in N3 = {378/567}, 7 locked for N3, clean-up: no 8 in R3C2 (step 1)
12. 27(4) cage at R2C8 = {3789/5679} -> R4C7 = 7
13. R345C4 = {257/347/356} (cannot be {167} because R3C4 only contains 3,4,5), no 1
13a. 7 of {257/347} must be in R5C4 -> no 2,4 in R5C4
14. 45 rule on N1 2 innies R3C13 = 1 outie R2C4 + 5, R2C4 = {89} -> R3C13 = 13,14 = {58/67/68}, no 4
15. 7 in R3 locked in R3C123, locked for N1, clean-up: no 3 in R12C1
16. R123C2 = {179/458/467} (cannot be {269} which clashes with R12C1, cannot be {278/368} which clash with R3C13, cannot be {359} because no 3,5,9 in R3C2), no 2,3
16a. 7 of {467} must be in R3C2 -> no 6 in R3C2, clean-up: no 5 in R2C8 (step 1)
17. 3 in N1 locked in R12C3, locked for C3
17a. 13(3) cage at R1C3 (step 4a) = {139/238}, no 4
18. 27(4) cage at R2C8 = {3789/5679}
18a. 6 of {5679} -> no 6 in R3C78
19. 6 in R3 locked in R3C13, locked for N1 and 25(5) cage, clean-up: no 4 in R12C1
20. 4 in N1 locked in R123C2, locked for C2, clean-up: no 8 in R5C3
20a. R123C2 (step 16) = {458} (only remaining combination) -> R3C2 = 4, R3C56 = [23], R3C4 = 5, R3C9 = 1, R18C6 = [12], clean-up: no 9 in R2C1, no 3 in R7C45, no 6 in R89C9, no 5 in R9C9
20b. 2 in N3 locked in R12C7, locked for C7
20c. Naked pair {58} in R12C2, locked for C2 and N1 -> R5C23 = [75], R5C4 = 6, R4C4 = 3 (step 13), clean-up: no 2 in R12C1
20d. R12C1 = [91]
21. Naked pair {47} in R18C4, locked for C4 -> R7C45 = [14], R6C4 = 2, R18C4 = [47], R12C7 = [24], R12C3 = [32], R2C4 = 8 (step 17a), R9C4 = 9, R12C2 = [85]
21a. 45 rule on N8 1 remaining innie R7C6 = 5
22. 27(4) cage at R2C8 (step 18) = {3789} (only remaining combination) -> R2C8 = 3, R5C78 = [31]
23. R8C6 = 2 -> R12C7 = 10 = [91], R3C78 = [89], R67C7 = [56]
23a. 45 rule on N9 1 remaining innie R7C9 = 7, R12C9 = [56], R1C8 = 7, R1C5 = 6, clean-up: no 2 in R9C9
24. Naked pair {38} in R89C5, locked for C5 and N8 -> R9C6 = 6, R5C5 = 9, R2C56 = [79], R46C5 = [51]
25. R9C4 = 9 -> R89C3 = 10 = [64]
and the rest is naked singles and a cage sum
9 8 3 4 6 1 2 7 5
1 5 2 8 7 9 4 3 6
6 4 7 5 2 3 8 9 1
2 9 1 3 5 4 7 6 8
4 7 5 6 9 8 3 1 2
3 6 8 2 1 7 5 4 9
8 3 9 1 4 5 6 2 7
5 1 6 7 3 2 9 8 4
7 2 4 9 8 6 1 5 3