Log output. From the coordinator on which I ran the command:

WARNING:  Do not have a GTM snapshot available
WARNING:  Do not have a GTM snapshot available
WARNING:  Do not have a GTM snapshot available
WARNING:  Do not have a GTM snapshot available
2014-02-21 16:31:37 PST dwheeler [local] 18075 5307efe9.469b WARNING:  unexpected EOF on datanode connection
2014-02-21 16:31:37 PST dwheeler [local] 18075 5307efe9.469b ERROR:  type "node_id" already exists
2014-02-21 16:31:37 PST dwheeler [local] 18075 5307efe9.469b STATEMENT:  CREATE EXTENSION nodeid;
2014-02-21 16:31:37 PST dwheeler [local] 18075 5307efe9.469b WARNING:  unexpected EOF on datanode connection
2014-02-21 16:31:37 PST dwheeler [local] 18075 5307efe9.469b LOG:  Failed to ABORT at node 16404
    Detail: unexpected EOF on datanode connection
2014-02-21 16:31:37 PST dwheeler [local] 18075 5307efe9.469b LOG:  Failed to ABORT an implicitly PREPARED transaction status - 7

From the primary data node:

2014-02-21 16:31:37 PST dwheeler 10.4.34.1(45626) 18077 5307efe9.469d WARNING:  Do not have a GTM snapshot available
2014-02-21 16:31:37 PST dwheeler 10.4.34.1(45626) 18077 5307efe9.469d LOG:  Falling back to local Xid. Was = 0, now is = 53146
2014-02-21 16:31:37 PST dwheeler 10.4.34.1(45626) 18077 5307efe9.469d STATEMENT:  SET client_min_messages = warning;

    CREATE TYPE node_id AS (
        customer_id INTEGER,
        username    TEXT,
        type        BIGINT
    );

2014-02-21 16:31:37 PST dwheeler 10.4.34.1(45626) 18077 5307efe9.469d ERROR:  type "node_id" already exists
2014-02-21 16:31:37 PST dwheeler 10.4.34.1(45626) 18077 5307efe9.469d STATEMENT:  CREATE EXTENSION nodeid;

From another coordinator:

2014-02-21 16:31:37 PST dwheeler 10.4.34.1(51612) 21621 5307efe9.5475 LOG:  Falling back to local Xid. Was = 0, now is = 53157
2014-02-21 16:31:37 PST dwheeler 10.4.34.1(51612) 21621 5307efe9.5475 STATEMENT:  SET client_min_messages = warning;

    CREATE TYPE node_id AS (
        customer_id INTEGER,
        username    TEXT,
        type        BIGINT
    );

2014-02-21 16:31:37 PST dwheeler 10.4.34.1(51612) 21621 5307efe9.5475 ERROR:  type "node_id" already exists
2014-02-21 16:31:37 PST dwheeler 10.4.34.1(51612) 21621 5307efe9.5475 STATEMENT:  CREATE EXTENSION nodeid;

And another data node:

2014-02-21 16:31:37 PST dwheeler 10.4.34.1(49818) 21622 5307efe9.5476 WARNING:  Do not have a GTM snapshot available
2014-02-21 16:31:37 PST dwheeler 10.4.34.1(49818) 21622 5307efe9.5476 LOG:  Falling back to local Xid. Was = 0, now is = 53155
2014-02-21 16:31:37 PST dwheeler 10.4.34.1(49818) 21622 5307efe9.5476 STATEMENT:  SET client_min_messages = warning;

    CREATE TYPE node_id AS (
        customer_id INTEGER,
        username    TEXT,
        type        BIGINT
    );

2014-02-21 16:31:37 PST dwheeler 10.4.34.1(49818) 21622 5307efe9.5476 ERROR:  type "node_id" already exists
2014-02-21 16:31:37 PST dwheeler 10.4.34.1(49818) 21622 5307efe9.5476 STATEMENT:  CREATE EXTENSION nodeid;

A third data node looks pretty ugly:

2014-02-21 16:31:37 PST dwheeler 10.4.34.1(51883) 26847 5307efe9.68df WARNING:  Do not have a GTM snapshot available
2014-02-21 16:31:37 PST dwheeler 10.4.34.1(51883) 26847 5307efe9.68df LOG:  Falling back to local Xid. Was = 0, now is = 53160
2014-02-21 16:31:37 PST dwheeler 10.4.34.1(51883) 26847 5307efe9.68df STATEMENT:  SET client_min_messages = warning;

    CREATE TYPE node_id AS (
        customer_id INTEGER,
        username    TEXT,
        type        BIGINT
    );

2014-02-21 16:31:37 PST dwheeler 10.4.34.1(51883) 26847 5307efe9.68df ERROR:  type "node_id" already exists
2014-02-21 16:31:37 PST dwheeler 10.4.34.1(51883) 26847 5307efe9.68df STATEMENT:  CREATE EXTENSION nodeid;
2014-02-21 16:31:37 PST dwheeler 10.4.34.1(51883) 26847 5307efe9.68df PANIC:  cannot abort transaction 53160, it was already committed
2014-02-21 16:31:37 PST   5162 53065e9f.142a LOG:  server process (PID 26847) was terminated by signal 6: Aborted
2014-02-21 16:31:37 PST   5162 53065e9f.142a DETAIL:  Failed process was running: CREATE EXTENSION nodeid;
2014-02-21 16:31:37 PST   5162 53065e9f.142a LOG:  terminating any other active server processes
2014-02-21 16:31:37 PST dwheeler 10.4.34.1(51844) 26776 5307ee22.6898 WARNING:  terminating connection because of crash of another server process
2014-02-21 16:31:37 PST dwheeler 10.4.34.1(51844) 26776 5307ee22.6898 DETAIL:  The postmaster has commanded this server process to roll back the current transaction and exit, because another server process exited abnormally and possibly corrupted shared memory.
2014-02-21 16:31:37 PST dwheeler 10.4.34.1(51844) 26776 5307ee22.6898 HINT:  In a moment you should be able to reconnect to the database and repeat your command.
2014-02-21 16:31:37 PST [unknown] 10.4.34.1(51885) 26848 5307efe9.68e0 LOG:  PID 26847 in cancel request did not match any process
2014-02-21 16:31:37 PST   5169 53065e9f.1431 WARNING:  terminating connection because of crash of another server process
2014-02-21 16:31:37 PST   5169 53065e9f.1431 DETAIL:  The postmaster has commanded this server process to roll back the current transaction and exit, because another server process exited abnormally and possibly corrupted shared memory.
2014-02-21 16:31:37 PST   5169 53065e9f.1431 HINT:  In a moment you should be able to reconnect to the database and repeat your command.
2014-02-21 16:31:37 PST   5162 53065e9f.142a LOG:  all server processes terminated; reinitializing
2014-02-21 16:31:37 PST   26849 5307efe9.68e1 LOG:  database system was interrupted; last known up at 2014-02-21 16:29:09 PST
2014-02-21 16:31:37 PST   26849 5307efe9.68e1 LOG:  database system was not properly shut down; automatic recovery in progress
2014-02-21 16:31:37 PST   26849 5307efe9.68e1 LOG:  redo starts at C/5BBA2688
2014-02-21 16:31:37 PST   26849 5307efe9.68e1 LOG:  record with zero length at C/5BBB53D0
2014-02-21 16:31:37 PST   26849 5307efe9.68e1 LOG:  redo done at C/5BBB53A0
2014-02-21 16:31:37 PST   26849 5307efe9.68e1 LOG:  last completed transaction was at log time 2014-02-22 00:31:37.34089+00
2014-02-21 16:31:38 PST   5162 53065e9f.142a LOG:  database system is ready to accept connections
2014-02-21 16:31:38 PST   26853 5307efea.68e5 LOG:  autovacuum launcher started

Curious that I have problems with no other extensions or loads. I will dig into the GTM warnings, though.