Habeas Litigation in the U.S. District Courts, by Nancy King, Fred Cheesman, Brian Ostrom. The full report is here, as a 127- page .pdf file. Some representative findings:

Capital cases were filed an average of 7.4 years following state judgment.
• Non-capital cases averaged 6.3 years before filing, longer than the average 5 years before AEDPA.
• Of capital cases, 4% were dismissed as time-barred under AEDPA's statute of limitations, compared to 22% of non-capital cases.
• Non-capital cases have averaged 11.5 months in federal court, capital cases have averaged 3.1 years so far (1 in 4 capital cases was still pending in late November 2006).
• Of 1986 non-capital cases completed other than by transfer to another district, only 7 received relief. Courts granted the writ in 33 of the 267 completed capital cases.
• The location of the case had a significant relationship to both processing time and likelihood of relief, after controlling for case-level factors.

Thanks to Legal Theory Blog for the link to the summary, and to Paul Weisser for the link to the full report.

  UPDATE: I have added the link to the full report.