We’ve been able to do MySQL 5.1 binary tarballs for a bit now (great working together with Kristian Nielsen of Monty Program), but packages are bit more tricky. Peter has been working on Debian/Ubuntu while I’ve focused on RH/CentOS. The following is from an OurDelta (trial build run) RPM install on CentOS 5 x64:

$ mysql -u root
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 1
Server version: 5.1.38-maria-beta1-ourdelta (OurDelta - http://ourdelta.org/)

mysql> CREATE TABLE test.t1 (i int) ENGINE=PBXT;
Query OK, 0 rows affected (0.10 sec)

mysql> SHOW CREATE TABLE test.t1\G
*************************** 1. row ***************************
Table: test.t1
Create Table: CREATE TABLE `test.t1` (
`i` int(11) DEFAULT NULL
) ENGINE=PBXT DEFAULT CHARSET=latin1
1 row in set (0.00 sec)

mysql> INSERT INTO test.t1 values (1);
Query OK, 1 row affected (0.03 sec)

mysql> SELECT * FROM test.t1;
+------+
| i    |
+------+
|    1 |
+------+
1 row in set (0.00 sec)

mysql> SHOW ENGINE PBXT STATUS\G
*************************** 1. row ***************************
Type: PBXT
Name:
Status:
090929 23:05:41 PBXT 1.0.08d RC STATUS OUTPUT
Record cache usage: 65675
Record cache size:  33554432
Record cache high:  65675
Index cache usage:  0
Index cache size:   33554432
Log cache usage:    295128
Log cache size:     16756712
Data log files:
1 row in set (0.00 sec)

So yes, PBXT is fully in there, as is XtraDB (the enhanced InnoDB plugin).

mysql> SHOW GLOBAL VARIABLES LIKE 'innodb_version';
+----------------+----------+
| Variable_name  | Value    |
+----------------+----------+
| innodb_version | 1.0.3-6a |
+----------------+----------+
1 row in set (0.00 sec)